I have had several Garmin GPS's, for running (Forerunner 301), for hiking (eTrex Vista), and now for the car. My dad had a Nuvi 350, which I used on a trip last week in NY. I loved it. Decided to get one for myself. CC had it for $300 on Friday, but I opted to go for the 660 instead, for $100 more. Its bigger, has bluetooth for hands-free phone, has better text-to-speech, and has the traffic features. I used it twice yesterday, and it is very nice. I am going on a workshop in Florida in 2 weeks, and this will be my primary mapping while I am there.
With the 660, I can download POIs and routes from my existing Mapsource software for my eTrex vista; but the software it includes is pretty good, and I doubt I will need to add stuff to it.
I do like the widescreen display - at 4 1/3 inches, its quite nice.
One of the differences between the 350 and the 660 is that on the 350 it would say "turn left in 500 ft," on the 660, it says "turn left on Baker Street in .2 mile." Its much more specific, and with the bigger screen, makes it really easy to navigate.