I use the MOOX builds of Firefox since they are hands-down the fastest out there with full pipelining support and custom tailored to high-speed computers on high-speed connections. (http://www.moox.ws/tech/mozilla/)
Now if Microsoft would finally get around to releasing a version of Windows that supports the 64-bit extensions for my Athlon 64 3400+ and I'll finally be a happy man (I'm tired of having to reboot into SuSE in order to take advantage of my processor's 64-bit support while rendering videos).
Sorry, that won't happen until Longhorn ships. By then you'll be shelling out money for a new computer since Longhorn will probably be tied into Intel's new Palladium chip.