I was working on composing large Bitmaps and scaling them and noticed an optimization that might have included a bug. The images I was scaling were pixel snapping and were not smoothed. This resulted in a choppy tween.
In the past avoiding choppy image animations required setting the quality to "best". Now ActionScript allows granular control of images. In my project they were embeded as external assets and pulled from a SWF file.
var bitmap:Bitmap = new Bitmap(_bitmapData, 'never', true);
bitmap.scaleX = bitmap.scaleY = .99;