I really don't understand why it's called "the birth of country rock." It's not even country rock, really, it's just straight country music that happens to be played by a rock band. But even if it was, didn't Buffalo Springfield lock down that genre like two years before Sweetheart came out?
Anyway, I think it's a thoroughly stale and sterile take on country music that mostly gets its stellar reputation from being one of the few country albums that rock fans bother to listen to. There are many, many better country albums out there. I don't really think it's bad - just really nothing special at all.