I don't like movies like this ... animated features, for kids, sappy. Spirit isn't bad for the genre, though. I liked the animation, which is old-school (i.e. usually not CGI) and often lovely. It's a nice touch that the horses don't speak English (a touch that's ruined, though, when Matt Damon does a voiceover narration as the title horse) ... (and why do the Native Americans speak English in this movie?). It's interesting that this "family" film takes the side of the Indians versus the expansion-minded American soldiers.
But ultimately it's just another sappy cartoon feature for kids. Worst offender: the Bryan Adams songs on the soundtrack.