The horses are very nice and amazingly realistic in their movements.
Do they react to the environment geometry convincingly as well by anychance? One of the beefs I have with a crapload of games with horses in them is that they either get aligned to the current terrain slope in a stiff manner, and that they freak-out upon hitting a wall, or keep running full speed into the wall while sliding by at whatever angle you hit it at.
Only game I came across with a horse that was convincing was Agro in Shadow of the Colossus, but that game had some of the best looking animations all-round of the last generation.
(watching a kid flail about with a proper sense of momentum and flow makes you feel sorry for the person)