I've heard a lot of good things about tom toms, however, I swear by garmin products. I must have had about six different types by now, different boats, hand helds even the palm pilot with gps built in. I have not gotten one for the car yet, but I find if you can use one garmin product you can use them all, they all work very similar, making things alot easier. Just my 2 cents.
Oh I did rent a garmin with a car a few months ago, think it was a nuvi forget what model number though. It worked great for the amount of time I needed to used it. Which was very little. It was when I went to Michigan to see the nuts in the Red Bull plane races...........