Setups and payoffs: in the very first moments, we see everything. Library, kid, "spoilers", and "death lends heft". The principle of script parsimony is in action-- everything tells, and most things have multiple uses. Data ghosting and saving to the computer pay off several ways (the creepiness of "hey who turned out the lights?" and the ending).
I like that Moffat seems to think about the interesting issues of the "time" part of "travels in time and space". He's shown us in a couple of scripts the way the Doctor is a prisoner of time's rules as much as any of us; more painfully, perhaps, because he violates them in some ways. But his own timeline is fixed. Ouch.
Lame writing: Underlining the point about what she whispered in his ear. Have her do it, have him return to it at the very end in his last conversation with her. Don't remind us in a heavy-handed conversation with the Red Shirt. (Successful writing: I feel guilty for not remembering the Red Shirt's name, because we liked her as much as the Doctor did.) Also lame was his failure to connect "forests" with "books" immediately, because, you know, Mr P and I did when we saw the title of the episode. The Vashta Nerada, or however it's spelled, were not very convincing. ("Blink" was way scarier.)
I remain unsure about the "everybody dies" versus "nobody dies" thing at the end. It was a bit of a retread of "The Doctor Dances", only without Eccleston's manic energy in the delivery. Tennant has a different kind of mania. This might just be "Nine was my first Doctor and I'll never forgive the rat bastard who replaced him" in action, though. The glowing white yes-it's-heaven thing at the end was a bit creepy. Who were the other two kids?
Professor River Song rocks my socks. Mr P had her pegged for a Time Lord early on, which I think was incorrect, but says she was successfully coming across as the Doctor's equal. Mr P thinks it would be best if she didn't ever appear on the series as a Companion, thinking it's more poignant if this is all we see of her. (Since there is so much of the Doctor's life we don't see.) But I'd be fine with a strong, intelligent, educated, daring woman on my TV screen a whole bunch. There are some very obvious hooks to hang fresh plots on here: what is the one time he'd tell her his name? what are the adventures they have together? And Moffat's in charge soon, so at the moment I'm betting on seeing her again.
Donna didn't have much a role in this, though she was given the traditional woman's role of "show compassion for somebody". Am not particularly gassed by the implication that all she really wants is a gorgeous guy who can't talk and then she's happy. Erk. River Song is way more my role model, thanks. Donna doesn't have to be like this, either.