TSC,
What version of FF are you having problems with?
I upgraded a very stable (but elderly and increasingly unsupported) 2.xx installation to 3.something, and it was - as you eloquently describe - a pile of poo, at least on my system / with my configuration.
I decided to go forward rather than backward, joining the 4.0 beta at rev. 2, and I have (as this thread attests) been impressed.
I run 4.0.8 on one home PC, 3.6.13 on another; I've got IE6 & IE7 at home also, and IE8 at work, so I've got a fair basis for comparison.
I might do a memory comparison between IE 8 / FF 3.6.13 and FF 4.0.8 when I have a little time.
I would still rate FF 4.0 as the best of the lot, with IE8 on a par / slightly above FF 3.6.13 (the others are for testing only).
I tried Opera, but found the lack of add-ons frustrating.
I've not tried Chrome - due to an inherent distrust of google's all pervading information gathering, rather than for technical reasons.
SD