I just downloaded IOS 5 and got the iMessenger app and am trying to register my username info so that I can start using it but it only gets as far as the screen that says "Registering" with the circle thing going round and round and won't go any further. I've deleted the app, re-installed it, turned the phone off and on 2x but still not working. Any help would be appreciated.
OP, you need to go read this. A lot of people are being confused. The new feature by Apple is called iMessage (not iMessenger) and it is built into the OS. You don't need to download anything from the App Store.
Imessage is an apple app, it comes pre loaded onto the device and it can not be uninstalled, to reactivate/activate Imessager
turn off imessage
turn off facetime
turn on imessage
turn on facetime
make sure send as sms is turned on under imessage.
make sure you are connected to wifi or cellular data.
make sure you are signed into Icloud.