Just a short notice, as I'm very busy: MM has posted a few quick fixes for IH2 which will be in the next bugfix release (which is still a bit out) at the breakmyzencart forums. You might want to check it out as it fixes the IE javascript error and the wrong referenced images in admin/preview. The tip with the png-compression should be
Code:
$quality = (int)$quality/10;
though (intead of 100), I think. (No guarantee, not tested).

Cheers,
Tim