The Beast Below maintains an honourable Nu-Who tradition. Specifically the second episode of any season being an absolute corker.
The Grand Moff once again goes to the RTD playbook and takes the new companion to a point far into the future of Humanity (presumable circa The Ark in Space time frame). In doing so he also FINALLY gave us a Space Whale in Doctor Who, some twenty-odd years after Davision was supposed to get one! That the Whale is also the Great Atuin is an additional bonus. There's hope for The Killer Cats of Gengh Singh yet (and no the cats of New Earth don't count, cool as they were).
The Doctor and Amy work far better in this episode too. There wasn't a whole amount of post regenerative trauma in the first episode, so the Doctor here is only subtly different from the Doctor of the Eleventh Hour. But we get to see him as the detective/problem solver that Moffat has always maintained the Doctor should be. Interestingly this is a Doctor who is a little more guarded around his companion than the nine and tenth Doctors were. Equally interesting is that this is a more secretive companion too. The Doctor once again hides and then brushes off the Time War (see The End of the World) and Amy has yet to reveal her impending marriage. Similarly they both hide their suspicions/knowledge of the enslavement and torture of the Whale from each other in order to protect each other. Amy certainly seems more like a person and less like a character description here. I also loved the Doctor's anger and his "you don't get to decide what I should know" bit.
The story is certainly stronger than The Eleventh Hour too, in that there actually is one to speak of. The only downside to this is that it once again taps into the Moffat trick of there not being a bad guy so much as a mistaken one and the Doctor saving the day by working this out. The Nanogenes in the Empty Child were trying to heal, but get it wrong. The Clockwork Robots were trying to fix the ship, but get it wrong. The Vashda nerada were displaced from their home and the library "saved" people to stop them dying. Here the humans misinterpret the action of the Whale and Amy works this out. This is no bad thing in as much as very few stories in Who's 40 odd years have played with this idea, but there is a risk of the Moff running it into the ground now that he is the head writer.
Moving on, I got a total kick out of the casting of this episode too. For a second episode in a row we got child thesps that can actually act, an Oscar nominee as good Queen Liz ten (gawd bless er) and Terrance Hardiman. The latter is the one I got a real kick out of as I have really fond memories of THE DEMON HEADMASTER. Sadly he didn't get a huge amount to do and wasn't the bad guy, but still THE DEMON HEADMASTER!
All in all a really good, if not quiet classic, episode.