I do all my embedded development in a Linux box so I can switch host OS (W7 or another Linux box).
Passing through USB devices has always worked for me with Virtualbox. I use it for PICKIT2, PICKIT3, ST Link, J-Link, etc.
So I wouldn't worry that W7 is not listed. As far as I know the biggest differences would be between XP and Vista driver model, but as they are both listed I am not worried W7 would work.
W8 may be a different, because it has had quite some changes on how strict it is with unsigned drivers. As long as they are signed it should just install I think (however I do not run/use W8 myself).