As I said the other day, the current cacheAsBitmap behavior has a few drawbacks which makes it nearly unuseful. As you know, the biggest problem of cacheAsBitmap is that the cached bitmap gets updated in memory everytime you modify it. In fact, only a translation on x and y axis does not update the cached bitmap in memory. A great addition in a future player would be locking the cached bitmap update in memory when the cached DisplayObject is modified.
The idea could be something like :
DisplayObject.cacheAsBitmap ( redraw:Boolean=true );
We could get huge performance improvements in terms of rendering in many cases, from game development to complex websites.
Please vote for a new cacheAsBitmap behavior, Flash Player engineers are listening