How much memory does your MBA have?
I've noticed that when I run my iSight all my MacBook Air gets slow, it happens in every app, like Skype, Flash on the Browser, Photo Booth...
There's not much you can do about it since your MBA only has 2 GB of system memory and limited graphics capability. Also, some apps like Skype require quite a bit of bandwidth to operate properly which will slow the machine down. Flash is another memory hog.
Is Leopard going to run it better?
Kind of hard to tell. You haven't told us what model MacBook Air you have.
- Nick
p.s. Running Snow Leopard is another possibility.