Yes, but twice the bit size means twice the reduncancy and twice the wasted
time on a cache miss etc. 64 bit Windows is by no means "twice" as fast ..
not at all. Furthermore, because one is dealing with 64-bit code the effect
can even be to halve the RAM. So a system with 512MB RAM acts more like one
with 256 because each integer takes 64 bits of the RAM now instead of 32
bits. But performance somewhat depends on the application(s), of course.
And drivers remain a problem because all manner of hardware "out there" is
not 64-bit supported. So whether they will work or not is dubious. 64-bit
probably will not get enough support to recommend it for at least a year, if
not more. So if someone sets himself up with 64-bit and has everything
running, great, until they go to the Computer Super Store next month only to
find nothing compatible.
There's no real reason to go 64 bit for day-to-day stuff. And those who
actually need 64-bit already know it.
64-bit XP/Server is for people who actually need it [and they know who they
are] and for computer hobbyists who enjoy a challenge. Business people who
need it to work now, gamers, emailers, surfers, web masters, newsgroupers,
and chatters etc. shouldn't care about it right now and might be better off
avoiding it.