Chrome at home, IE7 at work because I have to. 
I use Firefox 7 at home and at work. I occasionally use Safari on my MacBook.
Do you have the Add-on Compatibility Reporter? Most of the time, the supposed incompatibility is due to the add-on developer not including the appropriate version tags (or something to that effect). The only add-on I’ve lost that I really cared about was Google Toolbar; since I only really used it for bookmark access, I just located an add-on to show my Google bookmarks.
I generally use Firefox, occasionally Chrome.
Of course, Internet Explorer is the most secure, as confirmed by Microsoft evaluations. 
I used to be an Opera zealot, but each successive release added more suck and dysfunction. I have been using Chrome for a couple of years now. (And Chromium on my linux box.)
I use IE at work because our intranet database solution requires it, and once in a blue moon, when Chrome isn’t open already I’ll open a new tab in IE to look something up, because intuitively you’d think that’d be quicker and more painless than opening another browser. Then I am reminded just how much it isn’t.
I do wish that Chrome adopted the functionality of Opera’s “speed dial” start-up, and the ability to save window setups. I do sometimes miss that - but not enough to go back to having my browser randomly crash and burn for it.
Years ago I swore by Opera but at some point I phased it out in favor of Firefox. I now use FF 3.6. (I don’t like the newer versions.) I’d be lost without my Delicious toolbar, and as a contract web developer, Firebug is practically my best friend. Also as a web developer, having had even just a little experience with making pages cross-browser compatible, I am already starting to dislike IE a lot.
Firefox at home. IE8 at work, because we are not permitted to use others. The SYSOP at work insists IE8 is “much” more secure than the others.
Don’t like Firefox or Safari.
After an archive and install fixed LOTS of unhappinesses in my OS (something got corrupted at some point), I’m back to Demeter.
(yayyy!)
One thing I would suggest to anyone browsing on Windows is to browse in a sandbox. A sandbox runs the browser within itself and keeps the browser/Java/whatever from writing any files outside the browser folder. That should greatly reduce the risk of malware coming in through your browser.
Sandboxie is one such program that I’ve used and am happy with, I think Avast and some other firewalls have a sandbox as well.
The only complication I’ve seen from browsing in a sandbox is when you download files through your browser you need to review those files and specifically allow them to be written outside of the sandbox. Of course that’s just the sandbox doing its job.
Started using Firefox way backwhen it was Phoenix, used it exclusively until Chrome appeared. Now I go about 95% Chrome, 5% Firefox.
I used to know a girl named Demeter.