I use this with my HTC HD mini mobile phone, no data connection required for my phone (its a Pay as you go).
UK copy is alright, but I would highly advise against using US version if travelling. There are issues with maps that can be pretty lethal.
How so?
I know a few people who have used it, and have had a quick look at the reviews and haven't heard/cant find anything that states its "pretty lethal" in any way.
1. The thing insisted on entering motorway the WRONG way (against the traffic) 3 times, and once was nearly successful. I can't forgive that.
2. I have been taken to the top of the mountain and told to use a fire escape path as a shortcut. Luckily it was closed, but there were some interesting views
This is all Denver and Rocky mountains by the way.
3. Las Vegas. Why the hell did I make me go anywhere in the city via interstate? They are horrific places, nothing like M5 - 6-7 lanes and crazy traffic.
How long ago was that? I've just spoken to someone who has used it in the US in the last few months (the iPhone version), he had nothing bad to say, actually the comment was "just like tomtom, worked well".
Heavy on battery too, but you can do things to mitigate that and the heat issue, mainly get the screen to switch off over a set speed, this makes a big difference.