Only one star for this score?
In my opinion, the score is so simplistic and electronic because the movie didn't need anything more than that - a slightly funky, americana & minimalist score. I got the R2 DVD recently (with the isolated score) and it works perfectly in the movie, giving a 100% dialogue driven movie a good atmosphere. There's also several good string & piano cues you seem to have missed.
Maybe I'm a big Newman fan, but this score does its job and it a solid 4 star effort for me. You also mention the length of the CD? Well watch the movie - it's got less music than the CD does so I think we got a pretty damn good deal here.