The latest FF builds have been rock solid for me (Win7 x64 with 4 or 5 big name extensions and that's it). I've currently got about 130 tabs open, FF is using ~ 1.1GB of RAM and has been sitting open & running in this state for 3 or 4 weeks with no problems or slow downs whatsoever. The plugin container also finally works reliably so shitty sites with buggy flash code don't take the browser down when flash decides to…
In reality, Chrome is intentionally designed to slow users down by sending them to Google search results instead of directly to the destination URLs. People then click on the camouflaged AdSense.
Firefox is now faster than Chrome in independent tests, and it doesn't use up as much memory. Firefox is a much better browser in many ways.
Mozilla's big mistake is that they aren't reaching out enough to developers. It's developers who set the trends. Example: I started a Firefox developers group in the Bay Area, and no one from Mozilla replied to my messages about their helping out, even if nothing more than offering us occasional meetup space.