I've been able to confirm that the first beta (which is really an alpha, since it does not contain all functionality to be in the final release) of IE7 fixes all support for PNG. Otherwise, this version adds only the strange new user interface.
Also, no mention has been made about IE's irritating habit of downloading content it has no intention of using, such as scripts or stylesheets with an unrecognized MIME type. Try it! Create a page that references an external
<link rel="stylesheet" ...> with
type="application/x-ignore-me", then check your server logs (or point the
href to a script that sets a cookie, and check that). Despite the fact that IE knows it will not use the content, it downloads it anyway!