Love Firefox, and use it all the time when developing sites. I'm definitely not an add-on freak (though the Web Dev toolbar is amazing - Firebug's great, too), but I like its standards-support and cool icon. Beta 3 has made some good progress and is increasingly more Mac-like, but Safari's definitely giving them a run for their money. And who knows, maybe the next version of Internet Explorer (super-secret codename IE8) will prove a worthy competitor.

Ha. Sure.

P.S. John Gruber has written two great posts (here and here) about the latest versions of these browsers in recent weeks.