This device promises a lot, and initially seems good. The TV tuner works well, assuming that you have a good signal in your area. I live in a built-up area and can get a good selection of channels, but a lot depends on the aerial location. When i'm out in the country i've struggled to pick up any channels at all.
The sat-nav function seemed to work well initially, but the map isn't the most up to date and the 2009/10 update will set you back 150 euros. I've had inconsistent routing with it, where it takes me one way on the way there and then a completely different (and sometimes out of the way) route on the way back!
Most concerning is the support, or lack of. The VDO Dayton site only has a download section, there's no support contact on the site at all. I had a slight issue with the device when I first got it (user error) but couldn't contact anyone from VDO, and didn't get a reply from the UK support contact which i eventually found.
It's not bad, and i'm sticking with it for now, but i'm not sure whether i'd trust it to travel a long distance or abroad due to the inconsistent route planning.