I really loved the end of the tragicness of Doctor/Master - finally they're united on one side and one of them has to die.
I think that the graves can be taken as a conclusion that they ended up together. As for the rest - River could have gone back (at least I got that feeling) and the Doctor could always go back to before that point in time and arrange everything so it's ready for them.
Did you watch the Christmas Special yet? From that I got the impression that it's different incarnations of Oswin who remembers her past lives (only that her past lives aren't on straight line).