There's a message that comes up when you start MobileChat saying for the next 48-72 hours it might be a little buggy while they adjust the servers to accommodate everyone.
I apologize but I am a little confused. If your using it for AIM, is it different in some way or is it pretty much the same? I know with AIM you actually have to go into the app to see if you received any IM's. Is this app the same?