To be fair, one thing that NN has that IE just can't seem to get is the easy use of form commands to create guestbooks. Yes, yes, I know IE 4.0 and above claim to do the trick. It just doesn't do it with the greatest of ease. IE is seen as the leader between the two browsers. Lately, NN just seems to be playing catch-up.
People like to be with the leader rather than the follower.
In addition, although it was never trumpeted, the AOL browser was modeled after the IE rather than the NN browser. That's a pretty big endorsement. IE is interacting with me. IE 5's AutoComplete and drop-down location menu is great at remembering what I've previously written. I love the favicon.ico feature where you can set an image as your bookmark.