I am still on the fence about it. I am concerned that phone will become useless (like some iPhones 3G and 3GS on iOS4). Should I? What do you guys think? I am interested in opinions of iPhone 4 users NOT 4S users.
This is the best software update by Apple yet. Phone is much fester, pictures load faster, apps open faster, safari is faster, notifications are awesome, fast to take a quick pic now instead of going through to open the camera app, the list is infinite, and i haven't seen any battery decrease at all.
iOS5 might run even better on the 4 than the 4S, you got nothing to worry about.
You will love it.