So, people can iMessage you at any of the identifiers attached to you AppleID and it will be sent to all locations.
EDIT: probably shouldn't have fed a troll EDIT2: No troll here
But no worries, I'm going to replace it the coming Summer with an iMac 27"
Direct link for those having issues downloading...
For me it's nearly he same, the buddies window is exactly the same. Although they changed up how messages display.
You used to be able to not have windows grouped together (i.e. you could drag/drop different conversations out into their own window). You can no longer do that. You can move them to their own window, but if the buddy responds again it goes to both the 'main' window and the new window. Kind of weird.
I haven't really liked tabbed chatting, but I guess this may be time to deal with it.