I went from my 8100 blackberry pearl to an unlocked blackberry 8300 (curve) on t-mobile. I then went and picked up an 8gb Iphone and had it unlocked. It was a GREAT device, but for work and keeping tabs on my emails my blackberry just was unstoppable to be honest. The Operating system works flawlessly, the email setup is easy and push email is the best thing out there.
I got rid of the iphone and went to a t-mobile blackberry curve. I love it.
I may check out the iphone once the new series is released come December/January.