Found this just now:
http://www.otakutale.com/2016/sword-art-online-beginning-alpha-test-video-report/
Looks like the Alpha Test went well, though differently to how I expected. Looks like they'll need to do a bit of brushing up with the visuals and controls, but not *too* much overall. At this stage though, the only thing I'm wondering is how this would be implemented for home use. I was expecting that walking/running would be done via a control pad of some kind, not by actually moving around, even if that movement was done on a "multidirectional treadmill."