I have only once seen a UI animation that I didn't have to wait for. This was in the Metacity window manager, which had an option to animate windows minimizing/maximizing using a wireframe of their outline that could not be interacted with. The actual window moved immediately, and the wireframe did not obscure much of the screen while it moved. I would still turn them off, but if every UI animation was designed like this I would dislike them less.