The first part of this film was pretty solid: new centurion turns up at a fort, establishes himself, is wounded. It was like a 1950s western - you know, sensible and passable. Once the plot got going though, once the centurion and his slave boy venture north of Hadrian's Wall to reclaim the eagle standard, it all got exceptionally silly. Grown-up people would have plans and communicate them to each other. I also felt there was a kind of projection of modern western colonial privilege, but to examine this in any depth would be over-thinking it.
Part of the problem is that Channing Tatum is quite handsome but not too good an actor. The slashy story was ladled on by the hand of Marketing, and there was no chemistry. Before the film began there was some spurious 'Hollywood interview' with the lead actors and they were all 'I've totally got a man crush on him... it says here in my press notes'. Really, if you have to do this, do it with some conviction.
I don't want to be a total bitch, even though I am :-) Those who like Merlin and Robin Hood might well like this. I am guessing. It really isn't the thing for me.
Oh, the visual design was very good actually. I don't know if they brought in a team who are used to working together, or relied on one talented guy.