I've been a fan of Firefox for a while now (0.6 or 0.7) and love the browser. There are a lot of really great extensions, some of which you think should have been there all along and others which are amazingly useful but something I couldn't have come up with.
I guess about the font changes, I've noticed that Safari seems to render fonts with more weight (bold) compared to IE and Firefox - so perhaps that was a font issue and not a browser one? The fonts with Office are more MSey?? Not really sure as I recall Mozilla (plain) doing the same thing.
I personally browse the site using Firefox on Windows (occasionally MSIE 6.0x), and checked it on Safari on OSX (using
iCapture). I downloaded Netscape and Opera but just use them for dev purposes - a linux friend checked the site out on a few browsers on his box. Aaron does his best to keep it compatable with Netscape 4.x but I think that's kind of silly.