If I had to complain about one thing why I avoid IE7 and prefer Firefox it would be because of its way of handling tabs. I want to open new tabs when I type in a new URL, or open a bookmark, I want it opened in a new tab. Further I miss not having built in spell check like firefox. It goes of course beyond that, but these were my top two pains which made me choose FireFox. Just came across a link for IE7Pro which takes many steps towards coming close to FireFox (in my opinion at least). See screen shots below [via Public Sector Developer]

IE7 Pro
IE7Pro Preferences Screen