I don’t know whether there has been a miniature update for the mac version, but the game now DOES start on my MacBook pro. Performance is okay and mouse-operation (with a non-mac 3 button/wheely mouse) is okay.
I knew that the official release date was the 11th.
When Steam however showed the Mac Version as “installable” I incorrectly assumed (silly silly me) that it was released early. I think it’s rather stupid of Steam to show the “Install” and the “Play” button when the game is not available …