This is really exciting stuff. At the moment it's awful, the performance is just terrible in both HTML5 and the Flash outputs, but it's got a tremendous future if it be can be pulled off.<p>To a large extent it's already been done by HaXe but they have pretty severe marketing issues that have limited adoption.
Hmm the performance issues seem to be somehow network related. If you watch the clouds in the background they run smooth and the demo projects in the editor run smooth, too