@ Capt - we have Adam Smith's, so markets are free. libraries and cathedrals cost the same to build, produce the same amount of culture, but cathedrals cost twice the maintenance. So we build libraries first (well, most of us do - there are a handful of towns currently that inexplicably have a cathedral but not a library....

)
I'll probably finish 1260 AD today; depending on how long it takes, I'll post it just before pressing enter for comments. We still have space for more towns, though I haven't counted.
As for uni's, with the exception of a few already started at the beginning of my turnset (mostly aquaduct builds switched to uni's) I'm only building them in towns that can't draft and that can build them in 8 turns once they reach size four. Since a whole bunch of towns completed their cathedrals during Leif's turns, we're getting increasing numbers of towns giving us cannons and explorers for moveable shields (even excluding the towns building uni's), which will hurry the building of temples and libraries in new towns. We also will have a significant number more towns get to drafting in the next few turns.
@ Alan - thanks for the food analysis. I should note that it assumes that no citizens are working tiles of less than 2 food, a rule I've tried to enforce, but you know how these people are.

I'm glad that it looks like we have enough food for the required culture push.
I'm also reminded that many of our new towns need harbors in order not to be using low food tiles. I'm thinking at this point, that it's probably not worth building harbors any more in towns that will only get 5-turn growth; the 40 shields can better go to the temple or half a library. But if a town will get 3-turn growth (i.e., they have a fully-developed grassland available but the rest is tundra), it's probably worth it to build a harbor. But I haven't run the numbers.
Keep the comments coming!