Bug 721082 has changed perspective transforms; with rotation and perspective both mouse-hover detection and transition is broken. See the test case - you can find a small spot that triggers hover behaviour near the top centre of the purple div (the whole div should trigger hover), there is incorrect rendering when the div starts rotating and when it finishes rotating back to its original position. Rendering and hover detection are broken when acceleration is disabled. With D3D10 backend, rendering is fine, but hover detection is tempermental.

Thanks for the test case Nick!