From the ‘More Monkey Business’ files:
Firefox 18 is now officially in Beta and it is likely to be the fastest browser ever released by Mozilla.
When I asked Mozilla bout IonMonkey here is what I got back:
Linux users however have no such issue. Public releases of 64 bit Linux are available at: http://releases.mozilla.org/pub/mozilla.org/firefox/releases/latest/linux-x86_64/
So, if you want the fastest Firefox possible with the most addressable memory, you really want and need to be running Firefox on Linux.