I use Firefox and Chrome every day. My results line up with recent HN comments about how Firefox is competitive, uses less memory at scale (lots of tabs), still janks worse, but may be actually more stable at the moment. Flash is a big source of instability still, for both browsers.
My bottom line: both Firefox and Chrome are competitive, leading-edge browsers. Firefox on desktops is pure open source, Chrome is not (if that matters to you; it does to me a bit, but I'm a realist). AwesomeBar wins for me over Omnibox.
I hope you'll give Firefox a try again.
So, I just wanted to say thank you.
I wonder if you have a profile that goes back years and has some property that tickles a latent bug. Sorry if I missed it: have you tried running on a brand new profile? You'll have to use the -ProfileManager option on the command line at startup, I think.