Used the GM 24-70 & 85 for literally a couple of snaps each at a Sony event earlier this week. Big but easy enough to get on terms with and not imbalanced, which is a little surprising given the diminutive size of the A7x bodies. 85 snapped to focus in -4 EV (according to subsequent exif) but I didn't get to challenge the zoom with a low light AF test.
Also sat through a bit of a G Master presentation, much of which was the same stuff the press was briefed with previously. Of interest: Sony [rightfully] very pleased with corner sharpness full stop, but esp when compared to Canon & Nikon 'equivalents'. Same goes for CA and bokeh rendering. All the examples we saw and had the opportunity to try seemed to back up the claims, which leaves the 24-70 standing alone for quality vs Canon & Nikon. Similar situation for the 85. However, it has some acknowledged tough competition in the Batis, albeit their image profile is intentionally different. In the shared samples (at the presentation; I'm not prepared to share my images because they feature people) the Batis offers visibly stronger contrast whilst the GM has smoother fall-off and more consistent bokeh.
If I had to choose one of the two GM lenses it'd be tough. Obviously they're for different purposes and the zoom suits my needs much more clearly but I have a lot of lust for the 85.
It was also alluded to that there'll be a couple more E-Mount lenses announced/ released this year. No word on what, though.