Will give that a try, was thinking of doing something similar only trying a series of shots with it on and a series of shots with it off to compare. On my Nikons the VR in the lens is very noticable, was expecting something similar.

The vibration is the sensor. Since the A6100 does not have IBIS, you won't feel it. If you're seeing any stabilization improvement at all, it's the lens.  Zoom the lens all the way to 105mm and take a shot at 1/200 shutter to use as a control. Now slow your shutter down a stop at a time, starting around 1/100, then 1/50, then 1/25, etc. and see where the image is no longer sharp. That will tell you how about how many stops of stabilization you're getting with the lens at 105mm. 

So what would be your reason to wait for 'reliable reviews'? We already know where it's going to fall just by its very nature.  I'm currently not planning to preorder anyway, although I keep waffling back and forth. My practical side says summer is almost over and I won't use it much in winter, so wait until Spring and maybe it will go on sale. My GAS side, however, is far less pragmatic and wants to get one upon release. I checked with my local store who is a certified Sigma dealer, and they said they will carry them but they may not have them on the 25th. Of course, the other factor is availability. It seems almost every single release these days is followed within a week or two with a statement saying that the manufacturer has 'underestimated demand' and deliveries will be delayed. That's nonsense, of course. The reality is they don't want to build 10,000 of them and be left with 8,000 on a warehouse shelf. They've all engaged in this practice, including Sony, Nikon, Canon, and half a dozen of the Chinese companies.