1) Make the root renderer check all its sub-renderers' isActive state, rather than all the styleInfos, to determine if the main box should be created; this prevents the css3-container from being created and then not getting anything put in it.
2) Prevent the background and border StyleInfo objects from modifying the background/border runtimeStyle if that runtimeStyle has not been modified previously; also don't worry about resetting the border-style as that never gets modified when hiding the border.
3) Wrap several of the StyleInfo methods so that their return values are cached over the course of an update; gives a decent speed bump, especially now that isActive is called more often (see #1)
4) Move the attachment of event handlers down after the first call to update(); this prevents the changes to the element that occur during rendering from triggering update checks.
5) When handling onresize/onmove events, quit early if the element's bounds have not been previously queried; this prevents the extra loops which were firing after all the elements were initted when those elements have no initial CSS3 rendering.