I've been running windows 8 consumer preview since it came out, and well, I found that SL performs better on win8 than win7, at least using Exodus viewer. Between 5-10 fps more, which on my home parcel is a good improvement.. I have too many grass/tree prims.
The native win8 NVidia drivers havn't done anything I can see other than it just saying that win8 is actually supported by them.
Having said all that though, win8 has a bit of a learning curve. Lol I don't even know how to shut it down properly.. The button labelled "shut down" on the bottom/top right under settings kindly hibernates the computer instead, I'll have to google it again sometime.. Yeah, I know.. It sounds stupid, but I actually had to look up how to turn my computer off...
And cause it might make some better context~
CPU: AMD Phenom II X6 1100T Processor (3292.85 MHz)
Memory: 8186 MB
OS Version: Microsoft Windows 8 64-bit (Build 8250)
Graphics Card Vendor: NVIDIA Corporation
Graphics Card: GeForce GTX 550 Ti/PCIe/SSE2
Windows Graphics Driver Version: 9.18.0012.9617
OpenGL Version: 4.2.0