I dissent. Regretfully.

Rating: 6/10 (7 December 2017)

I wanted this movie to be great. It wasn't. The performance by Frances McDormand is good but not great. She's very good at showing overwhelming anger, but that's all she's allowed. Her character never gets the chance to breathe. Blame the script, not her--she's a terrific actor, but this is a one-note performance.
2. There is a sub-theme about race. Race is an important issue and deserves to be treated honestly, but in this movie, it felt like a side-road that led nowhere. (It actually feels like moral preening on the part of the scriptwriter. It didn't add much to the movie's meaning.
3. Wonderful performances by Woody Harrelson and Sam Rockwell as a police chief and officer. Woody especially brought grace to a character who at first seemed unsympathetic. (BTW, McDormand's ex-husband has a young and beautiful girlfriend, and that relationship is treated as awkward and shameful. Harrelson's wife is young and beautiful, and that relationship is treated as idyllic.)
4. Police officers don't talk like that among themselves or to others.
5. I particularly didn't like the Chief's take on racist cops, saying essentially that all cops are racist. That may be accepted as dogma by some Hollywood screenwriters, but any chief who talks about his beloved employees--or cops in general--like that shouldn't be a cop. Coming from this character, the sentiment is cheap and clunky and inexplicable.
6. There are a couple of plot holes wide enough to drive a billboard through sideways. The most egregious (no spoiler here) is what happens (actually what should have happened but didn't) immediately following the window scene. (You'll know the scene when you see it.) The thing not happening was necessary keep the plot going. Everything that happened after that feels tainted as artificial and contrived. Likewise a later scene in a bar, involving a coincidence beyond coincidence.
7. It's impossible McDormand's character wouldn't have been arrested several times in the course of the movie, for several serious crimes. Once again, he plot depends on that not happening, and thus the plot again is contrived.
8. There's a letter delivered to Rockwell's character late in the movie which is full of Hallmark Card sentimental drivel. It can't be justified by either what we know of that character or what we know of the writer.
In a world (as the movie trailers used to say) where we are awash in numbskull comic book movies and incoherent special effects spectacles, it was a small miracle this film even came to my local cinema. Too bad I couldn't love it.