DxO called the Sony Sonnar T* FE 55mm f/1.8 ZA Lens the best AF lens they ever tested. And indeed, it does perform very well on the A7 Mk II. The A7R with it's lack of an AA filter does produce sharper results but the files I got from the above combination are still pretty crisp. Even when I'm using the IBIS.
So you can see for yourself what it can do, I've shot four files that you can download (raw + jpg.) Two at f/1.8 and two shot at 1/15th. sec. You can download them HERE or click the image below. And yes my guitars are covered in dust. Makes them sound better!!