I think it hibernates just the kernel, so it isn't a complete reboot. I think if you choose restart from the start menu, it'll fully reboot. Shutdown hibernates it though.
Typically just Windows
I usually only reboot when I have an update that requires it
I have to reboot my air a lot more than I have ever had to reboot a window PC. Because of a bug that makes the laptop heat up to 80C without any CPU being used... and it doesn't go away until you restart.
I have not had that problem with my Air
But I reboot my work Win7 Dell constantly
My Win 7 box runs constantly. The only time it reboots is after an update which is pretty much the same as my Mac.
Wish mine did
My work computer constantly freezes
Outlook hangs whenever I try to do anything
Windows Explorer crashes on me
IT has looked at it several times and do nothing
Frustrating
I bring my Air to work to get things done
I have not had that problem with my Air
But I reboot my work Win7 Dell constantly