(available for purchase on Amazon.com, or instant through Netflix or Amazon Prime)
In the end, it's a really sweet movie, and it really gets the horse stuff on a good level. It refrains from over-explaining, which means that it avoids the pitfalls of getting the nitty gritty details wrong, and in its generalities it rings true.
You already know the plotline of this movie from a thousand other horse stories, but it's the way the movie treats everyone involved and especially takes its horses seriously, that really make it sing. That, plus the long, loving shots of 1970s fashion and horse equipment. Trust me, it's great.
This was also reviewed by Horse Nation and by Lauren at She Moved to Texas, if you'd like other opinions.