Here is what disturbs me about MSIE vs FF:
MS is a for-profit business and sells ad space - how good is their ad blocker going to be?
The last couple of evil exploits have been using click-through ads.
I use FF at home and I have no ads (sorry csgal - I really will contribute soon <vbg>) -- except that I allow google ads because they actually keep them corralled where I know what they are. When I have to use ie at work, the ads just drive me crazy.