I have had 3 BB's and will be moving to an iPhone next month. Check out this site for phone reviews. They are very thorough.
http://www.engadgetmobile.com/2009/07/01/sprint-matches-verizons-pace-launching-blackberry-tour-on-july/
They really like the Pre and iPhone. The BB's are no slouches either. I have a Curve now and use it for work so I'm on email all the time. I still think BB's are geared around email first and the phone is secondary. My camera is busted on it so I cant take pics any more. GPS and web interface is decent and I find myself using the GPS more and more.
If you will be doing mostly calls I'd find a more phone friendly device. Typing in a number you do not already have stored can be a pain and the QWERTY keyboard takes a bit to get used to at first.
I'm already on att so moving to an iphone is easy and I cant wait.