You seem to be the resident "look at me, I'm being paid by FireFox!" member, so I thought I'd ask you two things...
1) How do you set FireFox to open links in new tabs, instead of new windows? I have Tabbed Broswing and everything on, but new links insist on opening in new windows.
2) How do I set it as my super-duper default browser? Now, if I open GMail or Hotmail via the notifier or MSN, it launches in IE... and I want it to launch in FireFox. Possible?
1) Go to Tools - Options - Advances - Tabbed Browsing, and check 'a new tab in the most recent window', unless you've done this already and then I'm stumped.
2) Firefox should ask you if you want to set it as default everytime you start it up, unless you went and unchecked the 'Ask me this everytime on start up' box. If so, go to Tools - Options - General, and check the box under the 'Default Browser' heading. Then restart Firefox and click okay when it pops up asking you again.
1 - Lots of sites use code that will automatically open a new window. Since I usually middle-click on every link anyway, this really doesn't bother me. If you're having trouble middle-clicking (eg: no middle click) hold the CTRL key down when you click a link to open a new tab.
If you want a real plethora of tab options (so many its confusing and often hard to find that one option you're looking for) head on over to update.mozilla.com, and download the "Tabbed browser Extensions". Also check out a lot of the other cool extensions available, lots of them are really neat. I like Spellbound, myself, adds in-browser spell-checking.
2 - Firefox, last time I installed it on a fresh machine (that was version 9.3, IIRC) asks if you want to set it as your default browser, every time it is opened. If you said no, and ticked the don't bother me box, go: Tools > Options > General, it's the second up from the bottom.
Again, as they said above, many products (mostly microsoft products, that I've noticed) refuse to obey Windows' selection for default browser. This is usually because they integrate with IE for added functionality and security flaws.