I went with friends and liked the movie more than I expected to (I probably wouldn't have seen it on my own).
Agreed. I went into the theatre with very low expectations and was surprised. In fact, I liked it better than Superman for which I had very high expectations after all the hype.
Regarding the scent thing, I thought that was a clever way to solve the problem. And as one of the characters points out, animals have the same natural instinct to not feed on sick prey.