Yes, I have read it, thanks. I'll go back and have another look at it though. My hunch is that the main problem I'm having is not getting WebGL to work.
However, even on a slow computer I've had a noticeable further slowdown though.
I guess I can track the slowdown to one or more of a number of recent changes:
* Adding a small number of large sprites (300*300 say)
* With fairly large amounts of transparency (is overdraw an issue?)
* Significantly increasing VRAM (would this affect performance)
* Creating additional layers.