I have a UX31a and got it to work on Windows 8.1 w/ Update. You have to first update both the Intel graphics driver and the wireless driver.
Installing the latest graphics driver is tricky, you have to follow the instructions here: http://steamcommunity.com/app/233250/discussions/2/558749190911446231/
Both the graphics driver and wireless driver can be downloaded at https://downloadcenter.intel.com/
