Well! That was a lot of timey-wimey right off the bat.
So okay. As we know, River was in prison for killing a man. And we're clearly meant to assume it's the Doctor.
[spoiler]Given this, I initially assumed it was her in the spacesuit. Given that she seemed pretty surprised by the whole thing, I assumed that the "her" in the spacesuit was from her future. And given that we'd already seen her in prison earlier in the episode, this introduced the possibility that she was actually convicted and sentenced BEFORE committing the murder -- which sounds like a Moffat plot, doesn't it?
That's still a possibility -- after all, it doesn't have to be the same person in the spacesuit both times, does it? -- but for now we're left to assume that it is in fact the little girl, both times. And that she's probably Amy and Rory's daughter.
Plus, while the "I have a darker day coming" foreshadowing initially seemed to support my theory that River knew that was going to be her in the suit, it's much more compelling if what she told Rory is the truth: the day she dreads is Silence in the Library, an event that's already three years in our past. And it juxtaposes the (seeming) inevitability of the Doctor's death with the inevitability of her (sort of) death.[/spoiler]
The new monsters: Internet speculation, up to this point, has been that they are the Silence, or Silents, alluded to last season. [spoiler]One of them talks, which tends to undercut this theory, but[/spoiler] I'm still inclined to agree. [spoiler]Indeed I can totally foresee the Doctor or Amy asking them how they can be called the Silence if they talk.[/spoiler]
Anyhow. What can I say that's not Big Block of Spoilers? Great episode, great way to start the season off with a sense of urgency, a whole lot of weird and a whole lot of fun. Banter among all the players was great, and really you can't go wrong with Richard Milhous Nixon.
If I were to nitpick one little thing, it's that Washington, DC is hardly the only place in the country where you're going to see streets named Jefferson, Adams, and Hamilton.