My first thoughts upon watching the movie were:

-Why was it necessary to make her a "damaged" individual already, were they trying to excuse away her sub inclinations by saying she was already suffering from mental disorders?
-Why did they make him so stunted? I mean, the dom I know has never shown one morsel of regret for the way he is
-Dang! That's IT???? lol

After a few more watches, the movie totally and completely grew on me. I now view her character as being a person who needed to be a sub, but didn't understand that there were options out there that would bring her that release/pleasure/comfort without resorting to marking herself up.

And for him, I simply had never thought about things from the Dom's side. I can imagine that especially in this PC society, boys, then men, have it ingrained in them the "right" way to treat a woman. Beating them with a belt (albeit for mutual pleasure) probably goes against the grain for most men, and even if it's something they like, many probably struggle with being "OK" with it.

As for the "that's it?!?!?" bit; I appreciate the movie more now for showing the journey, or awakening maybe is a better word, in these 2 characters, and the ultimate message in the end that: IT'S OK. It might not be the mainstream, but it works for them, and they are happy.

Now if only I can convince M (coincidentally my boss) that we need to get out of our current relationships and just be together already like these 2 characters, life will be perfect!