Nelson mentioned the marvel of checking traffic on the iPhone. Nelson, I'm sorry - that's so last months future. Freeway traffic flows? Boring! I've only driven about 5000 miles the last year, and almost none of it were on freeways.
A couple weeks ago I ordered a Dash Express. Let me tell you: that is the future. The essence of the Dash is that it tracks your speed as your drive and uploads it to the Dash servers (anonymously, supposedly - they don't explain what they do to keep it that way) as you drive. Of course it also downloads traffic data from other drivers and historical data when no Dash owner has driven on a particular street recently.
It is so cool to watch. Entirely accurate? Not yet. Pretty darn good already? Check. A glimmer of the future? Definitely.
The Dash has wifi, but most of the time it uses GPRS for communication via Jasper Wireless. As a user you don't know that or even care, but as a geek it was fun to find out that there's a wireless carrier that doesn't do anything else than GPRS for mobile gadgets.
Since it's always connected they have built in local search via Yahoo local (not as good as YellowBot, of course, but pretty neat all the same ;-) ). They're working on giving you more "online data". For example there are gas prices and movie showtimes available, but the UI for that isn't very useful.
Dash are suggesting that the Dash Express will be the first GPS for "daily use" rather than just to be used when you are going somewhere new. it suggests multiple routes with distance and time based on current traffic. Pretty darn neat; but as I mentioned earlier - at least for my short-ish city-only stretches it's still not entirely accurate. I'm sure they'll improve on it though. The wonder of automatic software updates and constantly improved traffic data. I've noticed a big improvement in available traffic information just over the last two weeks since they started selling units to non-beta testers.
So to get better data it is of course in my interest to tell you to go buy one. In particular if you live in Los Angeles. :-)
If you are driving a lot and a lot to new places where you don't know the regular flow of traffic then I'm sure it's worth getting the first generation unit.
However, there's a lot to improve before I'm going to recommend it to "regular drivers" and non-early-adopter types. The physical form factor is, well, not really sleek. It's GIGANTIC compared to a modern Garmin Nuvi. They say it's to have room for the wifi and GPRS antennas (huh? The iPhone fits both a fraction of the space) and for the battery (which still only lasts a couple of hours; keep that 12v outlet available). The screen is a well working touch-screen, but the "hardware buttons" on top are crazy annoying when it's not mounted in the window or on the dash board.
Speaking of the screen - My first unit had a slightly defective screen, but Dash were great about getting it fixed and I could see that they had already improved their process on the replacement unit so it won't be an issue again. My second unit has been flawless so far.
Other than the issues mentioned above, it's mostly software improvements that are missing and those will hopefully be updated over time. It's done a bad job telling us a quick sequence of directions on freeways. It doesn't zoom in to show how clearly to navigate intersections or freeway interchanges. The UI is somewhat inconsistent (for example some buttons disappear when not usable, others stay on the screen and just "don't work"). It seems very slow at updating the screen at times. As I mentioned above the UI needs some work for some of the features to work better. Etc etc.
All that being said though - if you are in the market for a new GPS, give it a serious look. It's lots of fun and I trust the software will get better month for month. It will be interesting to see if or when Garmin catches up with the traffic data system or if one of the big players just goes and buys Dash. A device built with the Dash traffic data and with Garmins long UI, navigation and hardware expertise: drool. I guess if the Dash is the future; then that device is the future of the future.
Dash has a great help section that answers lots of questions in addition to their general feature overview.