If you watch the UI & Performance I/O talk given by Android framework engineers Romain Guy and Chet they actually hint at some of the under the hood changes in the next version of Android.
Those would be draw operation reordering & merging and introducing multithreading into the rendering pipeline. I could easily see those causing instability and battery drain in the latest unreleased version of Android. However, given they iron the issues out, I wonder how overall UI speed is impacted.