@Carol - yes, when I was using 3.5.x pages loaded considerably faster, that I can confirm.
The thing is that in the 3.5 line there seem to be some responsiveness issue, like when you click a link, it sometimes takes some seconds to "think" before it processes the request.
Or in earlier 3.5 releases, FF was halting for half a second every few seconds - it was noticeable when you were typing a long text in a textarea, or scrolling down the page (or doing other long, supposed-to-be-smooth motion).
At least until version 3.5.2, I know I was not the only one experiencing these issues, judging mostly by some long long threads on the Firefox message boards, which were followed by a fix version.
So yes, I am aware that some (maybe most) users do not see these issues - but still it is quite frustrating, as I have a relatively common configuration.