Zach Holman hypothesizes that the iPad's lack of multitasking as we know it — its single-window UI paradigm — isn't a bug, or just a feature, but the secret sauce that makes iPhone OS apps so tasty.
You play differently when you're on stage by yourself than when you're in a 300-piece marching band. Each breath you take — and each you don't take — will be scrutinized by an audience with its attention solely on you and you alone.
I'll add that composing this post right now could have been easier on a real computer (guess what I'm using instead), because task switching feels like it takes a lot of effort. Then again, I can't honestly say it was harder; it just felt harder because the one-window UI makes you painfully aware of the context switch. Which, like Holman says, may be the point.