Moose, I dont get the same behavior that you describe. It works fine (in IE and firefox) on diff. level 1 and 2. There in no decrease in performance ever. In difficulty level 3, with more pieces, the only time i see something that looks like a decreased frame rate is when I am dragging a piece very quickly over the center area of the stage (where you place the pieces), and only when i have filled that area with the pieces. AND it's not that bad at all: totally acceptable imo.

Hopefully more people will test it out for you, but unfortunatlyy (or maybe fortunatly) I am not seeing what you are talking about.