The Cersei/Robert conversation is arguably the best additional scene of them all, arguably because the writers actually knew the characters well enough to spin the additional scene.
It's definitely IMO the best scene they've done. The acting is brilliant, but not only that I feel that it makes the show characters better than the book characters.
I agree with both of you that it is a fantastic scene. But at the same time, it seems to me that if Robert and Cersei had enough meta-perspective on themselves and their marriage, they wouldn't be the characters we know. They seem to lack self-reflection necessary to actually have such discussion.
Very astute observation. Quite true.
"I can see it. You have more of the north in you than your brothers."