I use the Tab feature all the time in the latest version of Firefox.

Also, I like that you can adjust a lot of settings via:

about:config (typed into the Address field)

Firefox's extensions rock too!  Some very useful one's out there and they are so easy to add into the client.

Firefox handles all my activities save for when I am programming and when I have to access a set of screens when managing some servers I manage (it's actually a Java code problem).

Firefox!  *thumbs up*

I.E. 7?  I'm still looking forward to its release.  I'm open minded.... so I'll take a wait-and-see stance.