My company bought me a Garmin C330 to carry on trips. I use it in all the rental cars. It works well, the voice prompts are easy to understand. The POI database is sometimes a little dated. I drove to what was supposed to be a Hampton Inn in Kansas City only to find it was now a LaQuinta. There are POI sites to download specialty POI's though. You can't really go wrong with a Garmin, though I would try to get one of the newer, thinner models.
Good luck,