I wasn't too impressed with Hail Caesar.
There are two things to watch out for in more or less every single Coens film—firstly, the wholesale cannibalisation and loving reproduction of a particular slice of American culture, and secondly, a clever formalist or metafictional schtick that imbues the screenplay with avant-garde panache.
In Hail Caesar you've got "true life" Eddie Mannix in a Passion-like series of ordeals, testing his faith, as he struggles to get a film made about the testing of another man's faith.
I liked the film, lots of funny jokes, the communist writers were hilarious as was Channing Tatum's Gene Kelly-ish character, but I think the Coens really need to move outside their comfort zone.