Windows 8.1 has been out a few weeks now (and was on beta for months!) so come on Steinberg - does or doesn’t it work with Steinberg products? What’s the verdict? What are the common issues?
Sticky, top of forum. 
Which says relatively little other than “we’ll keep you posted”
I’ve not had any issues that I didn’t encounter in 8.
I see now I’ve read it properly. This is clearly not going to be an overnight thing.
I have extensively tested 8.1 with Cubase 7 and found absolutely no problems. I’ve updated all my machines. While there is no perceptible increase in DAW performance, overall the new OS feels snappier in file and desktop/windows operations.
Some glitches when double-clicking the title bar but I am still in the process of automatic maintenance, which can take some time.