Not that it really bothers me too much as a user, (since my primary browser has proper PNG support) but as a designer, my life would be made that much easier if MSIE supported the PNG image format correctly. So, without further adieu, I present to you the Proper PNG Support in Internet Explorer for Windows online petition.
I’m not sure if anyone remembers, but a while ago, I posted this image in an entry:
That is an example of why PNG alpha transparency is cool, and why no one really uses them yet. If your browser supports the format properly, you will see a penny sitting on the background color of the page (no matter which theme you happen to be using) without the anti-aliased “fringe” so common to transparent GIF images. If your browser doesn’t (*cough* IE) you see the penny sitting in a light-grey box.
There are work-arounds for getting PNG images to display properly in IE, but the methods I’ve seen thus far seem kludgy to me.