i used windows 7 drivers for my cintiq 20wsx until they released windows 8 drivers for it without any problems. i read some of the release notes for the windows 8 drivers and they have the same function as the windows 7 drivers + gestures and multi-touch support (for supported devices)
It works and luckily the weather wasn't as bad as I thought it would be. Phew least I don't have to down grade now. Tech support said they no longer support the 15x but I figured they'd say something like that.