I thought it was pretty much perfect.
[spoiler]Here's a noodler that I've been struggling with. The time-cops recognized River by profiling the TARDIS. This seems to imply that she will be the sole owner and pilot of the TARDIS during the time she kills the Doctor, since that's when she became the kind of criminal they track.[/spoiler]
Which brings us back to the question of where the TARDIS is when the Doctor shows up to get shot.
Also notable: [spoiler]seeing as she just leaves the Doctor there on the floor, we have absolutely no indication of how long she's in the TARDIS before she picks up Rory and Amy. It could have been minutes, or it could have been years.[/spoiler]
[spoiler]Also like that killing the Doctor alone puts you on the level of Hitler, because of his potential to save lives.[/spoiler]
Also neat that until [spoiler]they said "she"[/spoiler] I thought it would have gone the other way -- that [spoiler]the Doctor HIMSELF is history's biggest war criminal[/spoiler]. I mean, he kinda is.
ADDING: I really quite like the villains in the piece, too; there's something wonderfully base and horribly relatable about the notion that [spoiler]it's not enough simply to stop bad people from doing bad things, not even enough that they DIE, but that justice requires that they also be made to suffer[/spoiler].
Which brings up the question, what exactly does it mean to [spoiler]put somebody through Hell?
At a guess: preserving the deceased's consciousness forever, in a virtual realm of eternal suffering.[/spoiler]
Going to assume everybody can see where I'm going with this.