Works like it should (for the most part) Rated 4 out of 5 stars

This *does* make a difference for speed. But it depends on some things, e.g. which version of FF you have.
This ext does something sane for caching in older versions of FF, e.g. 3.6.x, but not so much in the newer FF5-11 because the handling of disk cache size has changed such that normally the Fasterfox setting for Disk Cache Capacity has no effect at all.

I'd not advice anyone with less than 4G of mem to have Memory Cache Capacity size set to anything else than -1 (= automatically calculated). The Piplining and Connections part of this work quite well!

But the rendering is a bit dodgy, there's almost never any point in setting the Inital Paint Delay to anything less than 250 unless you have a *really* fast PC and 100 Mbit broadband. Lowering it to 100 may be good in that case, but not less.

Since this exts Presets insist on setting some things to more or less non-optimal values, one needs to go into Custom and tweak stuff. And that's not very user friendly, so part of the point of Fasterfox fails at it is now. I still like it, having these options settings in one place where I can have a good overview of the perf affecting stuff -- therefore 4 stars

This review is for a previous version of the add-on (3.9.8.1-signed). 

about the calculating, it actually does auto calculate depending on your 'mode' you have it at