I have a Garmin eMap and I like it alot. It's small, very portable, clips onto a small dash mounted bracket (bracket available through Garmin) and they even sell brackets that allow the unit to clip onto a bike or motorcycle handlebar too. Good for boating too.
The detailed Garmin Mapsource 'Roads & Recreation' cd, which adds ALOT of map details to the GPS DLd from your PC costs $100 but to me it's very worthwhile.
My only complaints about the eMap is that it's screen is small (but still very usable) and that it's not color. They make larger screened color units but they're more $ and not as portable for other things such as hiking, biking, etc.
I have a nice newer laptop and toy with the idea of getting the Delorme GPS unit for it as it's a nice large screen, color, talks BUT you can't easily (safely) watch a laptop screen while driving w/o taking your eyes off the road and when traveling and stopped anywhere where you'll leave the car, you might not want to leave your laptop sitting there on the seat in plain view either wheras the dash units wouldn't be as tempting for a thief IMO.