Firefox blows loads of speedy load all over IE on older boxes, I used to run a 200MMX for one purpose, to play Wolf3D, it had Win95. I installed IE 6.0 on it (which I hear is impossible, but it seemed to work okay for me), which was really really slow at loading, it took around 3-4 minutes, which is nearly as slow as Mr X's wit. Firefox loaded on it in just under a minute, which actually suprised me, I thought they would be about the same. However Installing IE 6 downloaded like 110mb of shit, firefox was less then 10mb I think, cant remember.
Firefox is pretty good on an older machine, once its running, problem is it does use a lot of ram, that I dislike about it, however its fine on my laptop. I would also wish that they would change there makefiles or the SRPM specfile (probably the later) so I can build it for athlon.