Now that's what a love letter to fans and the show looks like B&B!
Everything but one thing hit the right note, the blubbing scientist wishing for the Doctor to save her (which she then did herself, which pretty much counters my annoyance at the scene).
Everything else (the humour, the character drama, the action, THE ENDING) was perfect. And I know it's a dirty word, but I actually enjoyed having the gravitas!
My fave episode since Parting of the Ways. In fact it may one up it.