The IE team had been heavily involved in XP SP2, rightly so, the even say that themselves. But they are now looking at gathering feedback for the next release. If you want to make an impact, head over to the  Wiki on Channel 9. I'd say: collect your top ten issues and make sure they are listed. Be as precise as you can be, no help in stating: Full W3C Compliance, specify which standards you want/need.

Since this is a wiki, you will need to look if your suggestions do not already exist, not just bulk-add your stuff.