Great for hiking and geocaching
I've been using this for geocaching for the last 6 months now, and once you've used this for geocaching (with a premium account), you won't use a non-paperless unit.

The unit is remarkably easy to use, thanks to the touch screen. This is a good thing, because the manual is very lacking. The screen is dim, especially when compared to the other non-touchscreen units. The only time you want the backlight to be set to less than 100% is when you're using it at night. It's worst when outdoors in cloudy days. When it is sunny, it is actually usable by angling it directly into the light.

I've had spotty performance when using this among tall buildings. And although it locks on to the signals and gives a position very quickly after power up, it may take a long time for the accuracy to settle down. I did notice that even when the reported accuracy is fairly large, the location is actually pretty accurate.

The strength of this one is to have almost all the geocache information when you're out hunting for the cache. Having access to the description, hints, and past logs can help enormously with finding the cache. It does require a premium account (you get a 1 month free trial after registering your unit with Garmin). You need to be connected to a computer in order to update the geocaches. There is no way to enter or delete geocaches from the unit itself.

At the end of the day, after you're done geocaching, logging it online is made much simpler by Field Notes. A text file on the unit records the geocache, time logged, and status (found, did not find, etc.) of your hunt. You can even enter a few words to help jog your memory - entering more text is possible but quite tedious. You can upload this file to the geocaching website, and have all your finds displayed on one page, instead of hunting them down again on the site.

As I'm writing this review, newer models with improved features are available from Garmin, but it remains a very good handheld for geocaching.

Excellent for Geotagging Photos
As an avid photographer, I use this GPS for geotagging my images with location information after the shoot. The Oregon 300 allows me to do this easily. I simply synchronize my camera's clock with my GPS's clock, create a new tracklog which updates at 1 second intervals, and start photographing. When I get home I use a software plug in for Adobe Lightroom to update my photos with GPS coordinates so I know exactly where each photo was taken if I want to return at a later date and reshoot. For a good source of topographic maps at no cost, Google "GPS File Depot". They have tons of topographic maps put together by fellow GPS users that can be downloaded and used for free legally--opensource rocks! They are compiled from existing topographic and geographic data by other GPS users and many times they have a higher resolution than commercial map products. Since they're compiled from the same data sources, they're just as good as the commercial map products.

Here's another tip: I have big fingers so it's hard for me to use the touchscreen for precise tasks such as entering destination points on the map. I went to a local electronics store to pick up a 3-pack of styli for the Nintendo DS for just a couple dollars. I keep them in my camera bag where I can access them easily. It makes using the touchscreen accurately so much easier. It also reduces fingerprints and smudges on the screen, which can make it harder to see in bright sunlight.

Superb hardware shadowed by software nightmare
HARDWARE
Oregon series feels sturdy yet light.
It is a beautiful device from a hardware standpoint.

SOFTWARE
We expect a modern GPS to do more than provide GPS or UTM coordinates. In 2010, there is a high expectation of convenient map management. Unfortunately, despite years of user criticism on numerous websites, the company still fails to improve its portfolio of applications to install (MapInstall and MapManager), navigate topographic maps (BaseCamp), route planning (RoadTrip) and training software (AntAgent). Will someone please stop this madness and integrate these features into a comprehensive Garmin application?

A typical outdoor enthusiast will purchase several topographic and road maps from different DVDs or MicroSD card.

NUMEROUS HURDLES:
-frustrating map unlocking system which fails to recognize purchased maps once some software component is upgraded.
-requires arcane Unit ID, Serial Number and Product Key/Coupon Code.
-USB map transfer is excrutiatingly slow, therefore, most efficient method is MicroSD card management...
-However, this faster alternative method requires micromanagement of filenames with arcane syntax conventions (gmapbmp.img, gmpapprom.img, gmapsupp.img) described on semi-obscure wikipedia websites.

BOTTOMLINE
-Garmin designed a beautiful GPS device that fail to live to its potential because of poor map management software.
-If all you need are coordinates to pinpoint your location on a paper map, this device is good yet way overpriced for its intended purpose.
-If you travel a lot and plan to install numerous topographic and road maps, expect to waste several hours managing maps, googling and contacting customer support.

Quality piece of equipment
I have owned this device, my first gps unit, for 3 months. It is a rock-solid device and has a very nice feel to it, a sort of tacky-rubberized band around the outside edge , which keeps the unit from slipping around in your hand. It has a crazy number of features and abilities, most of which I will never use. I bought it for off-trail hiking and it works very well for this purpose. I have read many of the reviews from other people and am a little surprised at all the moaning and groaning about having to change screens too often etc. People, this machine can point you to your car if you're in bumfreak Egypt from anywhere on the freaking planet! Get over the incredibly laborious step of pushing the touch screen a few times. On the annoying side I don't like the little paper "manual" that comes with the device. The actual manual is a cd. Good luck reading that in the field. I have called the Garmin help people and they answered numerous questions I had-they were very friendly to deal with. Also, I have noticed that the compass readings don't seem accurate unless you go through the compass calibration steps each day you decide to use the device. Again it only takes a minute or 2 to do so but, for the price of this unit you would think that the compass would ALWAYS be spot-on.

Oregon 300 vs Vista HCx
I have done an extensive evaluation of the Oregon 300. Here are my comments.

The Good:
-Touch screen makes entering and managing waypoints much easier.
-The car navigation screen is much larger and easier to read.
-The topo maps have the ability to be shaded in 3D for better situational awareness.
-The geocaching feature is superb. You have all the notes, logs, and hints right on the GPS while searching for caches. You can even record notes in the field (easy on touch keyboard) and then auto upload [...].
-heart rate monitor and cadence options are available.
-Profiles -finally. You can customize the multitude of displays and options and then effortlessly switch between them depending on your operating environment.
-Screen Capture - cool feature, but not sure I would use it much.
-Image Viewer. Resolution is okay, not great. This could be a useful thing to have though because you could scan a route description or detailed map, and then load it into the GPS for reference.
-Time Zones update automatically, or can be set manually.
-Backgrounds (desktops) can be changed to whatever you want.
-Wireless sharing of waypoints and tracks.
-WhereIGo Player for interactive game cartridges.
-Touch screen user interface is very easy to use and quite intuitive although some frequently used features are buried deep on some pages.

The Bad:
-First and foremost is the poor screen quality in medium light. The screen has almost no reflectivity and therefore under all but the brightest conditions, it is difficult to see without using the backlight at about 75% brightness.
-Because of the screen readability problem described above, and the need to use the backlight in most situations means the battery draw is significant and you can expect to only get about 8-10 hours battery life with normal use. Garmin says 16 but that is likely with backlight at 50% and timing out after 15 sec and using "battery save" which completely powers off the screen until you touch it. The HCx will usually go 25-30 hours by comparison because it almost never needs a backlight.
-There is no welcome screen. You lose it, you better have your name etched onto the back.
-The GPS cannot be used at all when connected to the computer. Also it powers off everytime you disconnect. (The HCx offers the option of staying on.)
-Basemap is not as distinct as on HCx. Water is shown in white and is difficult to discern from the cream colored land. However when in Automobile mode, water shows up blue?? (HCx shows all water in BLUE! Duh)
-No capability to measure distances or project waypoints using the map. (I use this feature frequently on the HCx to determine distance between 2 points, or to set a course.)
-Trip Reset is all or nothing. HCx allowed you to choose what you wanted to reset. On the Oregon everything gets reset (Except the odometer. There is no reset for that unless you restore to factory default.
-Track is only shown in Black. The HCx allowed you to change the color of the track.
-The alarm tone is very quiet and is virtually useless for me. No way to change it. (Also they eliminated the choices for what tone you wanted to hear for upcoming turns. Tones are either on or off.)
-Can't change the speed at which the compass turns off. The default speed is too fast. That means when you are walking at 2-3mph, the map jumps all around because the compass isn't stabilized. (The HCx allows you to change what speed at which the GPS references the satellites for directional info vs. Compass. I have mine set for 0.5 mph. That way it works when I am stopped and the compass is stable.)
-When viewing the Elevation profile, there are only 2 data fields. I usually set them to elev gained and lost. But then ironically, I can't see what altitude I am currently at. (The HCx has 2 fields at the top and always shows either altitude or baro pressure at the bottom.)
-Another major downgrade on the elevation profile feature is that when reviewing a profile there is no way to jump to that point on the map page. (On the HCx as you review a profile, it shows altitude, distance along the track. If you press enter, it takes you to the map page at precisely the point that you were looking at. E.g. When I am looking at the track from Mt. Baker hike, I can see precisely where I stopped to rest. When reviewing the profile, I could go to that spot on the profile hit enter and mark a waypoint at the exact spot we stopped. (Could save your life in a white out.) The Oregon has no such capability. That really sucks.)
-Heart rate displays only your heart rate. No max, no zone timers etc. Furthermore this GPS is NOT compatible with Garmin connect. WTF? Stupid.
-The unit retains the features for Area Calculation and best times for hunting and fishing. Why? I don't know. I have never used either one of those features.

Some general usability issues:
-The device has a rouded back and a metal clip for a carabiner. Problem is if you set it down on this rounded metal back, it will quickly slide off of whatever surface it is on. You could never set this thing down on a rock in the mountains. Your only other option is to set it on its face, but then you risk damaging the touch screen. That raised another issue. If a rock or stick or other sharp pokey thing was to impact or nick the screen, would you end up with a brick when you need it the most? (My HCx was in the lid of my pack when it went tumbling 35 feet down a rocky hillside end over end. I thought the GPS would be toast, but it barely was scratched. How would the Oregon fare in similar circumstances?)
-While the cursor on the HCx isn't as user friendly as a touch screen, it is MUCH more precise. Much easier than the Oregon to select and highlight waypoints on the map.
-Finally, while the user interface is easy to use, the organization of features is poor. All of the set up menus are located in one place which means you have to scroll through 4 pages to reach some of them. E.g the Altimeter set up is the 11th choice on the menu and on page 3.
So if I am viewing the Altitude plot on the Elevation Profile page, and I choose to view Barometric Pressure instead, I have to touch the screen a total of 10 times! (On the HCx, it takes exactly two key presses to do the same thing.) Garmin should have designed the software with CONTEXT sensitive menus that would give you all the options with one key press on the page you are viewing. Furthermore, to change pages you have to return EVERYTIME to the main menu where there are 5 pages of options. For the most part, this means 2 key presses to get you where you want to go. 1 to escape to the main menu, then one to select the next page. However if you select e.g. The Calendar on menu page 5 and then want to go to the map which is on page 1 of the menu, you have to press:
1. Escape
2. Left arrow 4 times
3. Map
That is 6 key presses.

On the HCx, pressing the page key twice will do the same thing.

Sensitivity and Speed
No contest. The HCx has the Oregon receiver beat hands down. Powering both units up simultaneously after they have been moved long distances and have to re-acquire satellites, the HCx beat the Oregon by more than a minute. I have tested both under the canopy of trees, and found the HCx is able to track your course more accurately with that highly sensitive antenna.

Overall, not a bad unit, but it could be so much better. If you mostly use it for driving and Geocaching, this is one of the best GPSs I have used. If you want to use it for more adventurous outdoor adventures, I would stick by the trusty HCx for a little longer and hope Garmin creates a unit with a brighter more energy efficient screen (OLED) and puts back in some of the features left out.