"The Impossible Astronaut" has some great parts, most notably Canton, the FBI agent with an attitude, and the special ability of the aliens. And some great visuals.
Increasingly, though, I'm feeling resistence to the series. I like (with some reservations) the companions, I like the latest Doctor, but Doctor Who has become an increasingly frenetic experience, with the focus on pace, pace, pace, a hook of mystery, and the ever-building mythos of the near godlike Timelord - such a far cry from the straightforward tales of the scientifically superior man with a time travel machine.
Each season the Doctor has become more special, the stakes have risen higher, the magical element increased. We're no longer saving mere Britain, or Earth, but the entire Galaxy! The entire universe! All of the Universes! And, uh, all of the universes AGAIN! And, oh no, the Doctor has died properly this time! Not. But he's dead this time! Maybe. Timelords are so SUPER SPECIAL that dozens of alien civilisations would invade Earth just to get a few cells of his body.
It's not that Doctor Who has become a bad show. Or even a different show. It's been reinventing itself for years, and it's only right that it should constantly grow and change. But it's become a purple show, some of the melodrama just doesn't work for me, and the season arc feels intrusive rather than ticking over with the current episode's plot. [I can cope with River Song, but only by mentally editing out certain portions of her. Rory redeems Amy for me, and I've given up thinking about how much more interesting the story would be if Amelia was the one travelling in the TARDIS.]
All this makes it sound like "The Impossible Astronaut" was a bad episode. It's not - it was fun, with a big hook of mystery and complexity. But I hope they take a step back from melodrama.