Amazing at first, but needs updating, and not worth the price
I got this when I moved to LA, where the traffic is flat out horrible. I first tried it with a free subscription, and it got me back to my house within 10 minutes when It would normally take me through this massive highway corridor downtown (the I110-I10-101-I5 merger) and saved me 20-30 minutes of waiting in traffic. I thought it was amazing, however since then, it often takes me on side routes where the traffic is far worse than what is happening on the highway, and that's because it doesn't understand or know if, when, or where traffic is taking place outside of the highway. The GPS always has a number of how many minutes you can expect to be delayed, but it's almost never accurate unless the number goes above 30-40 minutes and at that point you don't need to know specifics to wanna try and avoid that kind of traffic. If they could just either refine the estimated delay time (as it's NEVER accurate even closely) or add side street traffic, at least on major city streets like Sunset, Santa Monica, Hollywood, I would gladly pay through the nose for this thing, I can definitely say that until these updates are implemented, my subscription will not be renewed. While it is very nice to be able to see traffic ahead of you and know how traffic is all over the place, with a smart phone or iPhone, all you need to do is look at maps and get the same exact information for free, especially with the new iPhone 3GS being so reliable as a GPS unit and map updater.

A Technology waiting for Clear Channel TMC (in DC) and Garmin to Catch Up
I've had the GTM-12 attached to my Garmin Nuvi 360 for about three weeks in the greater Washington, DC area. I can only express my significant dissapointment in the execution of this product in conjunction with my Garmin. I would give this product one star, except it technically works to show traffic problems on an occasional basis. For most intents and purposes, it is completely worthless. Let me explain.

The primary reason to buy this device is to have the Garmin alert you to traffic problems and reroute you if severe, or at least suggest a reroute. First problem: Coverage. Clear Channel TMC apparently does not cover critical major highways in the DC area, such as 295 through DC. This isn't a minor oversight, it's irresponsible. Second problem: My Garmin doesn't perform any kind of traffic alerts even when facing severe congestion. For example, I travel westbound Rt 66 in the morning, a notorious A.M. bottleneck from DC to the split with the 267 tollroad (this road has traffic coverage). In my routing, I have a choice to avoid 66 if the traffic is bad enough. Even when the traffic map shows congestion and where I have an uncongested alternative (which is also has traffic coverage), the Garmin does not suggest the alternative. Third problem: the Traffic map itself doesn't adjust for your new position automatically. One has to keep selecting "Map" then "back" in order to refresh the traffic map. Annoying and dangerous.

To summarize, the combination of the GTM-12 and my traffic-enabled Garmin Nuvi 360 sufferes from 1) poor Garmin programming that does not properly suggest reroutes or gives you proper traffic alerts and 2) poor traffic coverage from Clear Channel.

Disappointing. HOWEVER, with some new programming from Garmin and better traffic coverage from Clear Channel TMC, this would be a tremendous winner. That makes the current situation even more disappointing.

Note, too, that you must have the unit plugged into power to receive traffic. Don't forget your charger.

BTW, I do not know if the newer Garmin Nuvi "T" units (with integrated traffic receivers) suffer from these problems.

traffic in the TV
Great - this garmin GTM 12 FM traffic receiver work around the world (only with my Garmin navigations-system). I use this receiver in Germany, France, Spain and Austria. In all contrys without any problems. The first 5 month in Florida - and whow - you see the streets in diffrent colour - with big traffic or free way.

GTM-12 for my Kenwood 5120, not perfect, but works.
I purchased this traffic reciever for my Kenwood 5120. It works, sometimes a little late, but it works. If I get into my truck and head out it takes a few minutes for traffic to catch up. Occaisonally, it will tell you as you are already in the backup. On other occaisons, it will warn you of the traffic that is 24991 miles ahead. I am assuming the planet is 25000 miles around. I am disappointd by the fact that this is a subscription service here in the states, it makes sense to have people aware of traffic and to try to aviod it. Saving wasted gas and extra pollution.

Nice Addition
Nice addition to my Nuvi 350! I was already mostly dependent on my Nuvi - it gets me anywhere! Now, I've got traffic updates... I especially like that I can see all traffic tieups (either text or graphics) - even those not along my route.

The reroute feature is not the best - but that's the Nuvi... the traffic receiver is small, easy to mount, and worked out of the box!