I thought it was a great reveal, and I particularly liked the Doctor and Martha's reactions.

That was an excellent episode. I can't blame Martha for staying behind, I probably would have too after all she'd been through, and you have to feel bad for the Doctor who'll be alone, though not for long I imagine.

Speaking of spoilers, sort of, I read on the BBC site that his next companion is going to be the same one he had in the first episode of the 3rd season.