Are you using linux, linux seems like a secondhand citizen with regards to firefox and that is where I see all my problems.
I don't know if crashing is the right word but it does become completely unresponsive often enough that it is noticeable and annoying. (Unresponsive as in it has to be killed to regain functionality.)
I've been using it -- on Linux and on OS X. I'm guessing that if I got more RAM, the "terminal unresponsiveness" would mostly go away. I've got only a gig in my old Macbook.
My favorite complaint is that firefox has become slower and more bloated over time.
I'd like to see such folk browse today's web with the original version of FF... :) The average webpage today is way more complicated than 10 years ago.
I don't know if crashing is the right word but it does become completely unresponsive often enough that it is noticeable and annoying. (Unresponsive as in it has to be killed to regain functionality.)