I find myself falling into the 4-star rating along with the [current] majority. As I enjoy Sean Bean movies, most of the time, I had reasonably high expectations of this one as he is a rather gruff Englishman portraying a knight, Ulric, in difficult and dark times as far as English history goes.
Whilst the story does not seem to follow any particular true history apart from the fact there was a plague in the 14th century, it does have a good gritty feel to it. The camera work is nice, and the locations were very suitable. The fighting scenes were quite bloody, and more grisly than I had expected, though given the nature of the movie fits in well rather than standing out as too gory.
I find it unusual that only Sean Bean is named as a leading actor. For me the story centered strongly on Eddie Redmayne as Osmund the young monk, who played his role very well throughout, rather than Ulric. Sean Bean did not disappoint, however, and the fate of his character came somewhat as a surprise. I was surprised to see Ian McInnerny (from various "Blackadder" roles) in this movie, although it took me a moment to realise who he was, as he's gotten more bulky in the last 20 years.
I agree with other reviews that the movies ends with an anti-climax - somewhat disappointing and leaves the watcher wanting when the movies actually ends, but does not ruin the whole movie by falling flat. There also seemed to be a build-up, when we first meet Sean Bean's mercenaries, of some form of iron maiden style device that can split a man in two, but its use is never implemented as anything more a cage. To me it was like waiting for a trap from a Saw movie to go off, and it never happens.
Worth watching, if you like movies set in medieval times. Expect no magic or witchcraft in this, it's not a fantasy movie.