Don't neglect Core Animation. Here is what I found, written by a developer, on http://theocacao.com/document.page/397 :
Core Animation is not just for fancy 3D effects. It's just as useful for 2D drawing. It simplifies drawing code (some cases, drastically simplifies it), and can provide huge performance benefits. If nothing else, Core Animation rendering runs in its own thread, so the UI can stay responsive while the main thread is churning away on something else.
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