this movie is not as ambiguous as some people are making it...
not ambiguous at all, frankly. for any textual unresolved conflict, there were plenty of conspicuous metaphors in the subtext.
john was smarter than caleb, and thus more worthy of ann, as intelligence tends to have higher intrinsic value than other traits, which derive their value from their utility in the context of either lesser or greater respective intelligent decisions. the most intelligent person in the room can probably find a way to make the lesser intelligent work for him. and thats what john did. no jealousy, played them both and then won in the end. caleb traded a night of sex for his life. bad play, showed his hand too soon.
this wasnt like mystic river or nothing, the predictable thing happened in the end; the better man got the girl. typical happy story. i didnt even feel bad for caleb, he was constantly characterized as a fox or a serpent.