I thought it was ok but that was mostly due to a few scenes, the stunning ciematography and a few rather scrummy actors (and sadly their time was brief).
I love horses, I have two, and they're my life, so I was expecting to weep. I really, really wanted to love it but for some reason it fell flat. Maybe it was the cheesyness of it, maybe it was the fact that I doubt a horse could go through all that and live, maybe it's because they made out that the guy that shot the dying horses was evil when he was doing the kindest thing, maybe it was the anthropomorphism. I dunno, it probably works better on stage without real horses as it was so unrealistic (a horse showing another horse how to put its head in a collar so it won't be shot? 
Really?) that it jarred. Also, I couldn't help but think that the horse was cursed! And it was the dad's fault, WTF was he thinking paying all that money for an unsuitable animal when there some beautiful Shires for sale? Plus the landlord was fairly decent, I thought, he did give them more time to get the money the dad had wasted.
I did have an issue with how badly they disguised all the different horses they used. In particular, the horse used at the beginning that was supposed to be a thoroughbred colt looked looked like a full grown cob type to me 
It was stunning, though, the cavalry charge scene, the 'over the top' scene, the gallop through the trenches were spectacular. I also liked the barb wire cutting scene, which I thought was quite sweet, and the opening scene with the foal which melted my stone heart a little.