I rented the movie on a whim, expecting it to be B-rated, but hoping for better nonetheless. It completely surprised me by having real depth and meaning.
The characters are complex and well developed -- you understand why they do what they do. The relationships are REAL, messy, emotional. Yeah, the story is based around the idea of a threesome, but there is nothing shallow about it. And there is no nudity, yet it still manages to be quite sensual, which I consider a compliment of the acting rather than any detraction.
For me, the thing that took this movie from okay to fantastic was how the characters reacted to the disintegration of the relationship(s). I don't want to give anything away, so I can't really say more about that.
The acting amazed me -- the three main characters were each incredible, and even the side characters had a lot of depth. You could sense the stories that didn't get told.