Commenting because I'm actually excited about this lens. Currently I shoot with an A7III I've had since release, the 70-200GM that I bought with it, along with the 85 1.8, the Tamron 2875 G2, and the 200-600G. I've been enjoying photography as a hobbyist since having kids, which are my main subjects (at performances, sporting events, general life, etc.). I'm pretty happy with the images coming from my kit for my needs, and have resisted the urge to upgrade. When the 70-200 GMII was announced, I had some GAS. As I have been shooting sports more recently as my kids get more involved, I have some more GAS for the newer tracking autofocus advancements.
I think it's been long enough and I personally would notice enough improvement in my images that it's time for a refresh, starting with this lens (and a new body, maybe the A7V if it is ever announced, or stretch the budget up to an A1II?).
Based on my usage, the 50-150GM would stay on my camera 90% of the time. I would sell the 85 1.8 and the Tamron, and pick up the 28-70GM, too. That, with the 200-600G, would make for a pretty nice trinity IMHO (although selling the 200-600 and replacing it with the 300GM and 2x TC is a move I would love to make if I had infinite budget). Speaking of the Tamron 35-150, the lens seems great, but am I the only one that thinks the lens has bokeh that is "panicky?" My 70-200's background rendering is creamier to me, for lack of a better adjective.
I tried a monopod and monogimbal set up for the 200-600, but honestly, hand holding is fine and I don't like the additional gear, so when people complain about the weight of these lenses, I feel like it's a big :-|.