IE7 Native PNG Support a Sham?
"This must be a bug in IE’s filter implementation. So what I did next was to test the same image with opacity applied to it in IE 7, since they now claim they have native transparent PNG support. But… the results were exactly the same. Which makes you wonder if it’s not just the same filter as in IE 6 being applied under the hood.
It has also been noticed that IE 7’s native XMLHttpRequest object isn’t really native. Did they just hack all the implementations?" [1]