Microsoft Update and Windows Update require IE, as do some other Microsoft facilities and a few web sites. IE is also extremely handy for editing your own web site's source HTML pages (if you've got one) with View > Source.
Otherwise, I always use Firefox. I'd advise you to try Firefox as it's free of charge, doesn't integrate with the operating system and you can always uninstall it or just ignore it if you don't like it.
I updated to IE7 a long time ago. There are no problems with it on my computer over and above those with IE6.
John