I run five instances of WoW using IS on a dual core laptop. Its far from an uber machine.

SUre, I can run my team through Dal, but I get 30+ FPS on my main everywhere but Dal and Argent Tourney Grounds.

I do have my graphic settings turned down in WoW.

The phenomena you describe in AV is unlike anything I've experienced. I used to get degradation after doing a window switch with KeyClone. That's never happened with IS and the speed is uncomparable.