Our team has basically abandoned Firefox in favor of Chrome. Our team consists of front-end, HTML/JS/CSS types as well as server-side devs. I'm surprised, but every member of the team independently has punted on Firefox. For some, it was the extensions. For others, it was the RAM consumption.
With the new release schedule, it seems every time I would open FF with a new version to pull, some extension no longer works. It's purely anecdotal, but it was enough to annoy the bejeezus out of us that we simply switched over to Chrome.
I abandoned Firefox for Chrome simply because it drove me nuts with software updates. It seems like every time I'd open up Firefox, there was an add-on update process and sometimes Firefox updates to install.
Chrome just stays out of the way and provides updates with all the crazy pop-ups.
The "default" today should be to install updates silently; not pester users with messages about why they should upgrade (I'm also looking at you Apple).
Firefox was becoming slow for me and a real pain to use, until I lowered the browser.history_expire_sites in "about:config" from 40k down to 10k. I'll probably lower it even more. http://kb.mozillazine.org/Browser.history_expire_sites
With the new release schedule, it seems every time I would open FF with a new version to pull, some extension no longer works. It's purely anecdotal, but it was enough to annoy the bejeezus out of us that we simply switched over to Chrome.