I've heard a few reviews that mention how fast everything feels. And the guys who are used to doing hard-core performance reviews acknowledge that part of this is single tasking, part is eye candy.

If the icon starts moving the second you touch it, and it takes .75 seconds to expand to full screen, you just gained .75 seconds in your app-opening time before people start to think it's slow.

This thing lives and dies on perceived responsiveness. Even if it takes longer to get to the end of an action, they want to make sure it starts immediately, in a way that's highly visible to the user.

In a multi-tasking windowing environment, Alt-Tab is an instant change. The iPad doesn't do that kind of instant. Instead of cut scenes, it does fades and wipes. I think the user experience they want to have is something like the Compiz effects, but that takes swap and video memory that the iPad just doesn't have -- yet.