Seems to run great for me. Running this on a HP dv6640us laptop, with 4 GB memory, and AMD64 Athlon X2 proc @ 1.8 GHz (dual core).
Linked the 6 GB swapfile I made for the 32-bit 5.9 Std to the 64-bit system for good measure.
The only problem I've had so far is when the PC compiled the Atmel drivers (from
http://at76c503a.berlios.de/) for my LinkSys 2.4G 802.11b USB adapter. It returned some unresolved symbols, but otherwise works. It's probably because these drivers are 32-bit, I suppose. Other than that, no problems so far. (The Broadcom drivers that come with this version still don't work for me...

But I've decided to pass on that for now. My laptop uses the Broadcom 4311 v.2 adapter that's built in. Works fine in Windows Vista, though.)
NVidia 3d for the 7150 chipset works great. The 64-bit drivers I'm using are the ones directly available from the NVidia website. I might be compelled to try out the Beryl 3d desktop here.

My projected uses for the 64-bit version might be for some scientific utilities, as well as maybe messing around with the Blender 3d graphics app.
Haven't tried any games yet, but I bet Open Arena will be a blast here. It's got 64-bit executables for single and dual CPU systems. Just need to copy that from Vista, over to the 64-Bit VL.