firefox slow rendering (e.g. wikipedia)

[Ian Malone]

Okay, I've had this problem for a while and I'm beginning
to wonder why.

Firefox sometimes responds very slowly, especially when
rendering Wikipedia and a few other pages (mostly wikis
actually). I don't mean connecting to the internet, I mean
responding to the user; e.g. I run a mouse gestures
extension which can become unusable with a couple
of Wikipedia tabs open. Booting the same machine into
Windows Me and running Firefox I don't have this problem.
System is FC5, Athlon 1.3GHz, 1GB RAM, GeForce 3 Ti200
with Nvidia drivers.

So:
Does anyone else have this problem?

Is this also present in FC6 (I will be upgrading shortly, and
won't bother with anything else if that will fix it)?

I've seen mention that this is because FC FF is optimised
for size, not speed, and various patches slow it down. Does
this sound plausible?  (I suppose it's easy enough to test
by downloading a binary FF from Mozilla)

-- 
imalone