The thing that set Firefox of is the tab windows. That's the reason why I use firefox.
IE7 have introduced these tab windows which will prove a huge hit.
However I've noticed after installing IE7 last week that the default font used in webpages for example the font this text is typed in has changed.
Not sure if I'm just the one or it has happened to everyone else. Hard to get used to.
Also the first thing I had to do once IE7 was installed was to edit the registry so that the menu bar appears at the top of the screen rather than below the url bar which has caused a huge upset for IE users.