I still have it running on the Monster. I'll need to get ready for the Beta to end and decide if I'm going Ubuntu (or similar) or buying a 4th Vista 64.
I really like it. Seems more stable than Vista 64, not that I had many issues with Vista. Folding worked perfectly, both on the CPU and the GPU. VM worked like a charm. I had Nvidia driver issues due to buying 4 GTS 250s before the W7 Beta drivers had support for them.
Over all, probably the first OS upgrade in a long time I'm actually looking forward to.