I have the U740. It's a great phone, but I wouldn't switch plans just for that phone. They full QWERTY keyboard is cool, but if you don't text all that much, who really cares. I haven't gotten good internet usage out of it and, frankly, I'm about to downgrade my plan because I never use "Vcast" or "Unlimited Messaging".
Granted, Verizon is not as anal as they used to be about where you got ringtones (I used myxertones.com to upload songs, edit it, and use it as ringtones). Also, you can of course add your songs to it and use it as an MP3 player (a pretty good one at that) But outside of that, you're stuck with Verizon's limiting offering of multimedia content.
As I said, it's a great phone. I like it a lot. But switch to Verizon only based on price and service, not the phone.