It's not the customization in itself - that would be inconsequential indeed, but the fact that if implemented right it hugely enhances the user experience. Like I said above, the app in Jelly Bean - in my experience at least - I've found it makes you want to use it. It's not that I can put this or that background but the general way it is implemented and my reaction to it tells me the Android team managed to get something sort of right. Apple can still care about "little things" like this without going against the UI "getting out of the way of the content". If the background can move around and that doesn't get in the way of the content, I think they can make Messages a little more magical (and I do NOT want to return to the skeuomorphism days, it just takes a little bit). Instead of ugly widgets or this and that, I've always felt the keyboard and the messages app are the best things that could be improved in future versions of iOS. It's stuff you are ALWAYS doing and that makes it of importance.