When I was at the Botanical Gardens the other day testing out the stills IBIS on the Sony A7 MkII ILCE-7M2, I also shot some video. This footage is all with the Sony SEL35F28Z Sonnar T* FE 35mm F2.8 ZA lens, which as you know has no built-in IS.
I edited the footage together in iMovie and used that apps. software stabilisation as well. The combination has produced pretty good footage, though the claim that the Sony A7 MkII ILCE-7M2 IBIS can stabilise walking footage is somewhat exaggerated as you can see.
However, for simple hand held video footage without a lot of camera movement it works very well. It's not going to beat a Steadicam rig though.
I would just show this footage I shot a while ago again.
This footage is off my Leica T (Typ 701), not what you would immediately think of as a great video camera. However, in line with the rest of it's innovative features it has software stabilisation, similar to what happens in iMovie, built into the camera. Again I've combined the camera and app. stabilisation and as you can see this is pretty smooth. And all without the need to add anything to the lens or to the camera.
I include this to pose the question, for the majority of non-professional video, might this be a better option? I have to say I was surprised and impressed when I saw what the Leica could produce. It's pretty basic video with few options, but it does produce decent smooth footage hand held. Just a thought.