This is what I did not like about the Captivate:
1. Battery life was horrible. Not even as good as my 1.5 year old iPhone 3G. (iPhone 4 is much better than both)
2. MS Exchange push email on Captivate was "iffy" at best. Sometimes it pushed, sometimes it didn't. (Both iPhones are rock solid in that area)
3. Charger wouldn't stay connected. (minor issue but very annoying)
4. Overall build quality. Nowhere close to any iPhone.
What I did like: the screen....that's all