We've had a few requests over the years to make Pale Moon available. Pale Moon attempts to achieve speed by sacrificing some important bits like accessibility, but fails to achieve this goal by pinning to the outdated ESR branch of Firefox. The result is that Pale Moon is slower than Firefox.
As an example, here is a comparison of the current releases of each, Pale Moon Portable 24.4 vs Firefox Portable 28.0. It's a fresh install of each before each test is run. Here are the results for three popular browser benchmarks:
PeaceKeeper (Higher is better)
FF 28.0: 2017
PM 24.4: 1461
CF 28.0: 1894
Sunspider (Lower is better)
FF 28.0: 267.8ms +/- 1.7%
PM 24.4: 301.3ms +/- 1.2%
CF 28.0: 291.1ms
HTML5 Benchmark (Higher is better)
FF 31.0: 7295, Total CPU Time: 14.46s, Total Lag: 168ms
PM 24.7.1: 7003, Total CPU Time: 14.84s, Total Lag: 210ms
Browsermark (Higher is better)
FF 31.0: 2481
PM 24.7.1: 2326
So, Pale Moon doesn't seem to offer anything that Firefox doesn't already have. And you sacrifice accessibility, compatibility, Firefox Sync, and quite a few languages in the process. I figured I'd post the comparison in case anyone wanted to see it side by side.
UPDATE: I added CyberFox 28.0 (CF) as well.
UPDATE (2014-07-24): To see if the above still holds, I tested PM 24.6.2 and FF 31.0 on the same hardware as the above with PeaceKeeper. PM scored 1575 while FF hit 2139 (higher is better).
UPDATE (2014-07-28): Since someone asked, PM x64 24.6.2 scored 1560 on PeaceKeeper. Firefox's x64 branch (which is what PM is) is not ready for prime time and will often score lower on some benchmarks.
UPDATE (2014-08-07): Someone asked about HTML5 Benchmark and Browsermark, so I added them in but with the current versions of the browsers. IE's Chalkboard test was also requested but doesn't make much sense to test since PM24 (and FF ESR 24) will be significantly faster than FF31 since they're based on an earlier version of the Gecko rendering engine and don't support all the CSS3 abilities the test is trying to run on them.