Well here's how it works....
First they have at least 2 or 3GB of ram installed, probably 3.
Then they have all the applications pre-loaded once before if not twice (meaning they launch it a couple of time and then quit it so it fills the ram)
Then they can simple launch any app they wish and it will launch on one or two bounces. On my MacBook Pro, Photoshop CS 3, launches in one bounce and Aperture with half a bounce.
As for the Video Chat, it's simple, the whole thing is done locally, and not over an actual internet connection where they are streaming the content limited by their upload and download speeds.
Otherwise I can assure you, that on a new MacBook Pro or an old one for that sake, the new Leopard actually runs THAT fast!
Another note to mention is speed of your HD and how much content you have one it. Also, depending on when you install an App, meaning where on the disc, it plays a tiny role to... Say you install Adobe CS 3 one year after you got your mac, then the content will be installed somewhere much deeper on the HD which in turn CAN take a little longer to access.. But, it's not a big deal...
So there...
It's THAT fast...