This is an incredibly disappointing app. Apple took something simple from the iPhone (text messaging) and screwed it up. Type iMessage into this board's search window and you get several threads complaining this app doesn't work.
It should work the way it does on the iPhone. When I see the same icon and label as on my iPhone, it should work the same. On any device I should be able to send a text (MMS or SMS) to any phone. It should have added the ability to send them to iPads. These should have been core capabilities.
Instead, it must be an iOS5 device that has to be registered and there are these silly rules for what address you put in it based on what device you are using. It does a verification that the address is registered that so far has rejected everything I've tried. Something as simple as sending a message from my iPad to my iPhone and it tells me that an email address I pulled from my contacts isn't registered. Both devices have iOS5, the email address was my MobileMe account that both have their mail apps synched to and they were both sitting on a WiFi. I even tried putting them on 3G. No change.
Maybe I can't send a message to myself; I tried sending one to my wife. She also has an iPad and iPhone with iOS5 and an email account synched to both devices. It seems my wife isn't registered either. I haven't figured out how to break the bad news to her. Maybe she'll take consolation in the fact that I too have been declared unregistered by Apple.
Seriously, thought, how did this pass Beta testing? How did one of the best programming companies on the planet not catch the problems in this? Apple needs to take a serious look at what went wrong. Somewhere their vaunted process broke down.
I'm going to cut my losses and put this app in a 'worthless app' folder and find something else.