Well, twice I had issues with firefox, at work, not going to any website after an update. I found other discussions on the web complaining about the same. Once I had to re-download the latest firefox (using IE) and reinstall it to get it back up and running. Second time it got fixed by itself (??) probably the re-boot might have helped or may be antivirus (avast professional) had something to do with it. Anyways it is no fun that firefox comes up with an update notification and after installing the update the whole thing stops working.
The instance where I switched to Chrome was when (again after an update) the firefox had issues at my home windows box.
So far my primary home machine, which is Linux Mint, never had any issue with Firefox. I install/update programs mostly from the repository, may be that helps. Not sure if they are far behind the updates.
I wish firefox won't be taken over by a bunch or marketing people. I see that trend in many places. Once a company or product starts getting popular recognition, a bunch of marketing people takes over the company to bring it to the "next" level. May be I am getting too old for rapid changes.
Edit: That being said, I should give credit where it belongs. Still firefox, when it runs (except after an update), is the most stable on all my machines (Windows, Linux Mint 14, Android 4.1). I don't see the message "He's dead Jim!", like I see in Chrome.