Good, not great. A bit disappointing.
Saw it in the theater. It was good, though mostly for cinephiles, but not great. A bit up it's own ass, some parts are hard to follow if you are not acquainted with the history of that particular time. Not as funny as I would have thought it would be, even though it tried to be. Thematically it seemed scattershot. Some characters and side plots seemed pointless, like the people nursing Mank back to relative health. What's it really about? A smart dude getting increasingly disillusioned with his job and the world (and getting increasingly drunk in the process) who then takes his anger and guilt out on who he thinks is the source of the evil permeating around him.
Will rewatch when it's on Netflix.