Also whoa, guess River's from two or three regenerations down the line then, huh?
Maybe. Suggestion seems to be that she's known at least one more version of the Doctor. (The reference to having pictures of all his regenerations could include earlier versions who she's never met.) It DOES seem clear that she doesn't know the ORDER of the regenerations -- which explains why she asked #10 if they'd done the crash of the Byzantium yet even though it's #11 she's doing it with.
At any rate, she doesn't know how much the Doctor knows about her. There's the exchange where they suggest he doesn't know who she is -- maybe he does and she doesn't know it, or maybe whatever knowing his name suggests is only part of the story.
...also, the Doctor's reference to facing the Angels a long time ago supports the theory that a whole lot of time passes between season 4 and the specials. It's almost certain that he's run into River offscreen at some point in there.
Anyway, very good; everybody really firing on all cylinders on this one. Fucking wonderful banter, the Angels as scary as ever (and with new powers that are a surprise but never feel like a cheat), and the mystery of River deepens. This is exactly the kind of thing I was looking forward to seeing in this season.