I have an At&t iPhone 4. One of my most frequently used apps is "Mark the Spot" and I wind up using it mostly for dropped / failed calls rather than slow data as I rely more on wifi. When I do switch, it will be when VZW brings back the $15 data tier. Hopefully by then my ETF will be down to something more reasonable. It starts out at $325 and drops $10 a month...
Perhaps I should mention I left a VZW BB 8830 for the iPhone. I had only one minor gripe. I liked the BB email a lot better. It is more flexible. For instance, if I forward a dozen emails to one box, I can reply as whoever the email was addressed to. Not on iPhone. I must reply as one of the accounts I happen to have set up on the phone. Not very convenient at all. I can use the gmail app to reply if I want but this really should have been part of the mail app on the iPhone. When I asked about this at the Apple store, they called it an "advanced feature." Yeah, right. Still I'm so happy I switched. Everything else about the iPhone is a lot better than any BB I have used. I would say apps is a very good feature. What good is it to have microsd expansion on a BB phone if you can't run apps from sd? Duh. So my lowly 16 gig iPhone 4 beats the crap out of a BB with a 64 gig Micro sd card (if such a thing existed).