IE 7 is now available for XP!  I've been using it now for a couple of months on both XP and Vista, and I think it's pretty solid.  This definitely brings IE back up to speed with modern browsers such as FireFox.  The only thing that bothers me is I can't set it up to automatically open a new tab when I type in an address.  I'm used to that behavior and I constantly clobber my tabs.  But, the streamlined interface, real tab support, and improved performance really make it good.  It really shines on Vista.