I'm not saying things aren't incredibly responsive, but some of the animation techniques are used brilliantly to disguise lag.
Three examples:
1. Mobile Safari doesn't wait to render what it hasn't downloaded/formated before responding to touch gestures. You swipe and the page scrolls. It might display a checkerboard before it catches up with rendering, but the swipe command takes precendent.
2. Those wizzy transitions when double-tapping the home screen, or returning to the spring-board. They start immediately and actually mask what's going on behind the scenes with regard to processing a request. They're the ultimate illusionist progress-bar. And they need to be tuned finely to present the illusion or else it becomes obvious that they're masking tactics.
When people complain about the performance of new iOS versions on older devices such as the 3G, what they're really noticing is the illusion has been broken as Apple is optimising and fine-tuning the illusions for the latest hardware.
3. Those screengrabbed snapshots of apps that have been completely closed and display when an app is restarted. If the load time is short enough, the illusion of instantly re-entering an app is maintained, even if all you're seeing is a stale image of the app your closed earlier.
I'm not sure if Android employ any of these tricks, but they demonstrate the focus and undocumented nature of Apple's drive to create the illusion of perceived GUI 'smoothness'.
Not only that, but I'm convinced that users are actually more efficient when perceived responsiveness is added: for instance, most users will not start thinking about what to do next on an app until they are seeing the app interface; presenting then with a non-interacting screenshot as soon as possible actually makes the overall interaction more efficient. But the ultimate is what the guys making PCalc discovered ( http://www.dragthing.com/blog/2009/07/how-to-make-your-iphon... ): you can put a non-interactive screengrab in such a way that even though it is a dumb image, touches will actually be recorded and have their effect as soon as the actual interface is set up; users can actually interact very soon. Now that's badass.
(however, most animation stuff doesn't fall in the category of perceived responsiveness, as most often, for instance for transitions, the end result must be ready before the animation begins; also, "undocumented nature"? Apple's obsession with perceived responsiveness is well-known).
(You are right about the other things you objected to in my comment.)
