Yes, it is unique to the MacBook Air now because the new MacBook Pros are not out yet. Of course they will have it too. All Macs will. They will come out with a new mouse for the desktops too. Wait and see
This is all going to slowly be added in to get people use to it and with 10.6 we will see some serious Multi-Touch going on. Then windows will have theirs out 2 years later in Windows 7 with lots of trouble trying to get hardware to implement it after Apple has had it in their mobile devices and computers for almost 5 years LOL 