I have two iPhones 4 and an iPad 2. I've been able to iMessage between the two iPhones. But to and from my iPad I hadn't been able to get it to work. I use my iPad primarily at home, and I've had this problem over two routers and two Internet service providers. I made a Genius bar appointment re this problem, and while waiting I hooked up my iPad and iPhone to the store's wifi, and lo and behold, iMessage is working. The Apple store guy had no suggestion other than to reset my network settings. But when I got home, the iMessage was working fine with no need to reset anything. A few hours later, it stopped working, and continued to stop working until I hooked up to another wifi network. When I got home, it worked again for a few hours until it stopped again. Weird, huh? I read somewhere about opening ports and the like, but this wouldn't explain why it works at all, and works on my iPad only after it has been hooked up on another wifi network. Any thoughts appreciated.