Of course the other thing about the snap feature is that widescreen is now so prevalent, and you can use it to divide the screen in half easily. I'm writing this on my huge barely-small-enough-to-be-called-a-laptop, and have a TV program running in a window that's snapped to half the screen, while using the other half to surf.
I did some testing of other apps that have "non-standard" GUIs. One (SonyEricsson PC Suite) supports Aero Snap totally.
Another app supported it partially - to my surprise. It supports it for maximising and minimising, but not for snapping to the sides of the screen.
A couple of others only supported it for minimising. I guess because they're not windows that can be resized.
I couldn't really see any developer documentation about it, though. I guess there must be some kind of windows event raised when you press the key combinations, though, so you'd at least be able to intercept those and get a partial implementation.