I have one of these. For a basic GPS, it works great. It lacks some advanced features, but for the price, who can complain? Lack of unlimited map updates kinda sucks, but it's never been a problem for me.
Not the best GPS in the world by any means, but for the price, it's absolutely worth it. Might also be something good even if you have something better, to bring with you on trips for in the rental car.