IE just sux in my opinion and I find that Opera is faster on my desktop than FF but lately I've been using FF more often only because I'm on the tablet and haven't d/l'd it to this yet. Don't really want any extra stuff going on on this one because it's a work pc.
I use Opera desktop mainly for the Opera Link features. My bookmarks are synced to my MyOpera site and are accessible from Opera Mini on my BB. I also like to store and sync notes. As others have stated, I find Opera to be faster than IE.