I thought it was fine, which is to say better than a lot of recent attempts at pre-black powder historical epics, but not as good as the ones I enjoyed growing up and as a young adult.
I think that in the end it just felt very by-the-numbers, and also much more limited in scope than I had expected. I had kind of hoped for something that covered a longer period of time and ended more-or-less with Scottish independence (which to be fair would have to have covered most of his reigh, from what I gather), and instead we kind of just got the opening shots culminating in one big surprise victory for the Scots.
I also felt like in a couple of instances characters were lacking sufficient motivation for their actions. Two stand-out occurrences of, to me, unjustified "changes of heart" seemed forced for the purpose of pushing the plot forward or contrived suspense.
Anyways, all in all I didn't feel like it was a waste of my time, but I don't know that I'd recommend it or re-watch it anytime soon, either.