The ending is kind of contrived. Rosalene insists on not telling Watts that she believes River will reappear, for no reason other than that it would undermine the impact of that very moment on the player. Spoilers, by the way.
Oh yes. And at the end where River took so long to turn up! I think what finally broke me down is when John and River were holding hands in the spaceship just as the flatline started. Knowing that the scientists were just playing with memories and that it never truly happened like he'd wanted at that point.
I both hate and love that. I mean, it sucks that it never really happened, River died without John even remembering WHY he wanted to go to the moon... But it's also wonderful that he got his wish fulfilled in the end.
If only River would've been a client too, I would've been satisfied.