I've been looking for an alternative to all the nightly 64bit F builds doing the rounds here and there for a while now, and the one thing has has been a constant was their lack of any improvement in any way.
So I tried again for whatever reason>. can't really remember, maybe something to do with Java(64bit) .. can't remember.
So I went searching, and in that searching, I came across an offshoot branch, which is called WaterFox (### I 'spose!! )
If you're currently using FF(the official version of 15.01 is still only 32bit), then the switch to WF which is at v15.0 will be easy.
As it's FF based(but a 64bit build), it uses your current FF personal settings, so the change is simply install WF and you just have a 64bit version of FF(called WF) at your disposal instead.
If you try Waterfox and it doesn't work for you, and then decide to uninstall it, do not remove all personal files and settings! You lose them in FF as well, as they're linked to the same settings files.
So far that I've noticed, it is faster than FF(32bit).
I've cleared the cache a few times now, and it still feels as fast in loading (all pages) irrespective of whether the cache has been cleaned out or not.
FF on the other hand feels slower to load pages if cache files are cleaned out(I use CC Cleaner to clean out temp files too .. not FF itself)
... anyhow, just a heads up for those looking for not too different alternatives!(to FF that is).
I have no idea on how it will work with any extensions and addons you have installed, but so far non of my 10 or so addons and extensions were rejected as 64bit incompatible.
I'd rate it a recommended install for anyone running a 64bit OS, if not for the adventure, then more so for confirmation that it feels snappier than FF.