David Tennant gives a fucking transcendent performance in this one, too. Really worth seeing, even if you have no other interest in Doctor Who.
And yes, it's nice to have a Doctor who isn't all hugs and bunnies again. People forget that despite his quirky space drifter persona, he's basically a fucking god, and gods get wrathful sometimes.
To back up ROUS's awards claim I know that the two halves that make up this episode were nominated for the Hugo this year for "best science fiction TV show" or whatever the category actually is. The episode that won was another Doctor Who episode "Blink" which is just amazing.
Blink was pretty cool as well, though my heart belongs to that lady who had so much plastic surgery she was just a stretched flap of skin on a metal frame.
I liked this because for a moment the series gave the Doctor back some of the underlying "don't fuck with me" that was always present in the old series. I like Tennant, but his Doctor is far too continuously whiny about violence and "humans are so violent" etc.. Baker and Davison pulled that off without sounding so....pretentious, I guess.