You couldn't get much better. The subtle body language between the two actors, the great dialogue, Wonderful interaction with the therapist...it just doesn't get better. I only gave it a low score on special effects because there weren't any...you can't grade what's not there.
To me, there were only two places where the movie fell down. During the therapy sessions, Arnold references a time when Kay said no to sex. He says she was the first one to turn it off and it was for "years." But there's never an explanation. Then, when they are in the nice hotel for the night, there is the moment where he "stops" and she begins to cry. At first, I thought this was a good moment, because she mentioned in the therapy session that he always kept his eyes tightly closed during sex, never looking at her. And here he was, looking at her! So it took me a bit to realize that something went wrong there. Less subtlety would be better, in that case.
But it's a lovely movie.
Pros well paced, great story, great actors, honest