This right here. uMatrix makes the difference for me between usability and non-usability of FireFox-variant browsers. This is true whether I'm using Intel or PPC. Unfortunately for PPC, Firefox variants are all we have left in the browser space, at least on OS X. This very forum is worse than unacceptable, it's downright unusable (quite literally) for me with T4Fx on any PPC system, unless I'm using uMatrix. @defjam, if you never tried uMatrix or something like it to tame the javascript and other garbage code all over the web, then your experience is understandable.
On a 2 GHz G5 w/ TFF FPR19, I've been purely relying on a customized version of the MVPS hosts file + foxPEP 1.7 all this time, and have been seeing reasonably good performance on those two alone.
After reading this comment, I decided to put uMatrix 1.1.4 back for the hell of it, and it's made the Web that much more usable, even after the aforementioned additions and all.
So, I would certainly say those three ought to be a borderline requirement when expecting realistically usable, even good performance from TenFourFox, each serving a purpose of its own.
MVPS hosts removes the ads and their scripts, foxPEP accelerates image rendering, video playback, and site loading (plus a ton more), and uMatrix blocks the remaining third-party script cruft. With no hardware acceleration, the result must be seen to be believed.
Matches made in heaven.