If you are either buying a new machine or have decided that now is the time for an upgrade to your rather slowexisting machine - then 64 bit is worthwhile.
You are future proofing your investment by having a machine ready when the 64 bit applications come along, in the not to didtant future.
If you are just upgrading because you just fancy the latest technology while having a perfectly adequate machine then I would say not, wait and when you really need an upgrade you will get a faster better spec for the same money.
I've bought an Athlon 64 based system and it's as good as any p4 system i've seen.
bremner has got a good point about future proofing, but i heard a nasty rumour that Windows 64 will only be available on an OEM licence (i.e. you will only be able to buy it with a new system). Not too sure how much truth is in this
Why spend a wedge to get a task done by your PC in a few milliseconds faster.Above 2Ghz,a home user is unlikely to be able to see much difference.Bit like american cars,massive engines but lousy performance. :-)
i had a 2700 xp and last week upgraded to thr amd 64 3200.
On the 3dmark03 benchmark, designed for gamers, i got an increase of approx 400 points. The only game which i have noticed a difference is flightsim 2004 in the loading times. Apart from that halo and all my other games run the same.also an athalon 2700xp will cost you £80quid(i'll sell u my olf one for £45).
I'm using an AMD64 3000+ in my mesh system and am over the moon with it, the price I paid £999inc vat for the system including 17inc LCD N'vida FX5900 and loads more over 5months ago I think is great value for moeny and would buy it again.
When 64bit longhorn comes out online retailers will supply it on oem and ill upgrade to that with an extra 512MB RAM.
Regards to the processor I might upgrade it in two years to the most powerful 754 socket I think is the 64 3400 and will be happy with that.