Anand said it's the best mobile OS yet, and the hardware is great aside from average cameras, a poorly designed charging port, and horrible HDMI output.
He also alluded that Office 2013 Preview tends to max out the CPU, but he didn't notice any other perf problems.
A Windows RT OS review is forthcoming, so no comments on the software.
I admit I was disappointed to see much better performance numbers from the Atom-based tablets running Windows 8. It makes me wonder why MS priced the Surface at $500 when Atom-based tablets are around the same price with the full x86 compatibility.