One thing I like about FF over IE is how it identifies more username/password combos than IE does. I love the save login info feature, and IE7 identifies most of them but not all, like my bank's website. Is there any way to force IE to save that information for sites which it does not prompt you for?
Besides that, I think IE7's interface and tab and bookmark implementation/handling is much better than FF's. It's just all around easier and quicker. And I know people will contest this, but in my experience IE7 defintely loads some pages noticeably faster and with less delay than FF. Not all sites, and not all the time, for example after a page has been cached, but enough to annoy me.
For me, all FF has over IE7 is the better recognition of username/password combos, and the spell checker.