I did some research on software and driver issues with Win 8 Pro prior to moving to it, and had to perform a reset to defaults step in X2 after installing the latest Presonus AudioBox 1818 VSL audio interface, but other than that everything runs great.
Please do be advised that as of yesterday's site info, DPC Latency Checker reports incorrect latency values due to some internal timer changes with Win 8 that they have to adjust for with the software.
Latency Mon (I think it is what is called) gives correct values, plus a bunch more info.
I happen to like most things about Windows 8, although some things are in the annoying stage - little things about how to do old familiar stuff.
So, my advice - use either one, but prior to switching, do your homework on your software/hardware environment and its compatibility with Windows 8.
Bob Bone