I use Firefox on my main computer and Chrome on my Netbook because its got a smaller address/tool bar so I can see more of the page on the small screen.
Opera, FF, IE8 - in that order. Opera works well on 99% of sites i visit, and is faster in producing active content than most other browsers i've tried. Used to use FF for everything, BUT i found that "stop-and-go" sh** it pulls (3.5 does it) when loading image heavy pages unbearable. IE8 is better than IE6 and IE7, and is compatible with most things... so when i see something being incompatible in Opera, i fire up IE8. as for Chrome, i used it for about 2 minutes when it just came out, didn't like it, and ditched it. I found that most of the stuff that works in Opera works in Chrome as well, and if i am forced to chose a 4th browser for my web dev stuff, i'd chose Safari. Firstly becaus ei think it's unbelievably crap, secondly because if i had to consider most of my clients' target audience, i'd see that Safari is more used than Chrome.
Firefox, but I also run Chrome, IE, Safari, Netscape as standard, but I would run anything else as I like to check sites i've made across them all.
Used Firefox for years but I tried Chrome when it came out and haven't looked back. Had a couple issues with Hotmail after launch (which I figured was MS being bitches, it only stopped working after a week or so) but everything works fine now. Never had forum issues or anything like that. Its fast, and for running on a widescreen takes up the absolute minimum screen space.
Firefox - ABP, Fireftp and Firebug are a requirement for proper web design. BTW Quakelive is the best time wasting plugin ever.
Chrome here. Sleek easy to use. No clutter in the interface whatsoever or to tweak or furnish the interface just to make it work well. Just love it especially when reading regular feeds via Google Reader.
Firefox generally. Only drawback is that FF tends to leak memory like there no tomorrow. Safari is great too, it's much quicker than Firefox (native 64bit I suspect) and has a smaller footprint. Only thing there is I haven't found an adblocker yet (to be fair, I haven't bothered yet). If they could combine the two...
+rep. Probably want to avoid 32-bit in Snow Lep, but since I haven't upgraded yet, it's no biggie. Thanks!
Opera for me, since 2001 or thereabouts. I use IE only for the few important sites that don't work with Opera. I try every new version of IE, FF, chrome, safari etc, but none match Opera for speed, UI and efficiency. Opera 10 is hands down the best browser I've used.