iMessage can't fail. its not really possible. if you have an iOS 5 device and the other person does too it gets sent via iMessage. if one of the two people don't then it gets sent via text. the phone does everything for you. all you have to do is type and send. people might not use it as much on the iPad or iPod Touch but it will get a lot of use.
was thinking the same thing. if apple could license iMessage to the biggest smartphone vendors (Google, Microsoft, Rim, HP) then it would be taken care of. I think a lot of people would like this. I mean RIM might not take it because of BBM and Apple probably won't but i think it would go far.