ah, I see. managed to get pooling up for the arrows in Invasion... not convinced that I've gained any framerate (maybe a tiny bit), but it definitely no longer judders every few seconds from the GC.

http://www.birchlabs.co.uk/Invasion5Pooled.swf
http://www.birchlabs.co.uk/Invasion5NoPool.swf

(also, fun result from when I forgot to reinstanstiate gravity: http://www.birchlabs.co.uk/Invasion5Fun.swf)

Can you explain this whole BitmapData.lock() and unlock() thing to me? it sounds like it's something I should be using.