The workarounds (editing the .inf files) do not work with the final 8.1.
We have to wait for the final drivers.
As Windows 8 appeared, Roland delivered the new drivers in a few days.
The Quad Capture came within a few hours.
 

As described within the VS-700 section of this Forum, I got this to work ... using the .inf patch. 
Needed a Workaround of re-starting Win8.1 with mode 7 (Driver signing mode) for the "bcdedit -set TESTSIGNING ON", but everything (VS-700C, VS-700R dual) works great with final Win8.1, X3c, Cubase 7.06 & Ableton Live 9.0.6
 
Do not have a VG-99 to test :-(
 
Starfield