o.k, I hate to disappoint you but there is only one thing at the moment where 64 bits is awesome:
Scientific Applications
I could real off a whole load of programs while if you've played around with on previous computers you'll notice a huge increase in performance on 64-bit multi-core CPUs, not least of which is the new Mathematica 6. However, almost nothing else is compiled for 64-bit because the performance advantage is negligible when the hardware emulates 32-bit so well.
Though I do have to say, I notice a slight speed improvement especially when multi-tasking in XP x64 vs. XP Pro, but that's not really comparable because XP x64 is really just Windows 2003.