The Harry Potter references were hysterical, and given that JKR is supposed to be a fan of Doctor Who, I like to imagine her falling off her sofa laughing so hard. And honestly, who doesn't love the idea of Barty Crouch JR shouting "Thank you JK!"?
Some of the best dialogue shown in the whole show ever. The running gag of random Shakespeare lines popping up and Shakespeare deciding to grab them. "No, you can't have that one. It's someone else's." All going back to the whole 'power of words' theme.
"Hey! I wrote that!" *snerk*
"Don't rub that - you'll go bald."
"57 academics just punched the air" - The really, really scary thing about that reference? It's not based on a random number of academics. Shakespeare's Sonnet 57 is widely believed to be addressed to a man, with this being why a number of academics question Shakespeare's sexuality. Yes, I know too much at times. [/geek-mode]
"Expelliamus?" offers Martha at the end, thus proving that, yes Doctor, she does say the right things at the right time. :P
And the Rose references, while nice, are staring to grate a bit. The reference while Ten and Martha were in bed together was nice, logical and heart-warming (loved Martha's huffy reaction and blowing out of the light), but the later reference with the witch was just annoying.
Which Queen of England should the Doctor piss off next?
Overall, much love.