I've been using iMessage a lot more than whatsapp ever since it came out. I only use whatsapp for people who still haven't updated to iOS 5 and for people on blackberries. Two things that whatsapp does better is the way you hide the keyboard. Tapping the chat seems much easier and tidier than flicking the keyboard down in iMessage and having to scroll back to the end of the chat. Also, it's annoying how there's a bit of a delay between sending messages on iMessage. I know it's less than a second but on whatsapp u don't have to wait for the message to float up to chat so you can start typing the next message. I hope Apple addresses these two issues. I feel like they haven't put much effort into the UI of the app. Same old Messages app but now you can hide the keyboard and not have to go out of the chat and back in to hide.