Reasons For Android Lags
Android's primitive garbage collection, which practically forces the OS to constantly kill off apps running in the background to reclaim their RAM, coupled by the real-world problems of trying to use a phone's flash to do Linux-style virtual memory.
That's why some Android home screen-replacement apps use 3D acceleration, but become fuzzy during transitions... they drop the resolution and color depth down to what the chips can handle, and don't go back to full-resolution until the transition completes. You can see it for yourself... do the "rotating cube" effect (or whatever you want to use), and notice that the moment the gesture begins, the resolution gets fuzzed in half, then snaps back into focus when you stop.
If you can think of anything else please do share it in the comments.