I have used GPS Navigation for 4 years now. And have recently purchased a new system by Navigon. They are the only manufacturers that I know of that incorporate "Reality View". When coming up on interchanges on a highway or freeway, it will change the screen to look like what you see out the windshield. ie. Large green highway signs, all the lanes off traffic, which lane you should be in... it is very clear and helpful when you are approaching any interchange. I have found it quite helpful.

Anyway Navigon has 3 different models you can choose from. All of them have real time traffic control available (the entry level model offers it as an option you buy additionally)
www.Navigon.com will show you what I'm talking about.
www.tigerdirect.com offers a multitude of GPS options for you to consider.

PS. keep in mind, not all GPS units will actually speak the street names.