Very gritty and realistic, unfortunately it suffers from being SO realistic that it just isn't a particularly entertaining movie to watch. Doesn't paint the supposedly elite US troops in a very favourable light, either.
But, the fact that all the 1 star reviews are from people touting "Lone Survivor" and "American Sniper" as great war movies (2 works of absolute fiction), and can barely write in comprehensible English, should tell you all you need to know.
There's also one particularly funny review below from a man saying that because he's played Battlefield 3, he knows what combat is like.
Ignore these idiots and watch it yourself to form your own opinion.