Depends what you're after, m8.
If you're after gaming, probably not. About 95% of stuff is written purely for 32-bit anyway, so XP64 makes little difference. There is a small, but steady supply of developers supporting it now though - that and dual-core processors too. Still rare though.
The biggest benefit you'll have (if you need it, that is) is that the memory limit of 2GB per process is no longer there - as in XP32. If you need apps that require more memory, XP64 will definitely give you benefits.
It's actually Windows 2003 Server at it's core, not Windows XP 32-bit with bits bolted on.
I have my home PC as a dual boot XP32 and XP64 machine. Best of both worlds. Vista can stay where it is for now!
D.