Hi,
If any of this info is old, sorry, I haven't read this forum at all. I only lurk in the Noble's Club threads.
I saw the first showing Saturday morning. Culture borders don't pop as in the past. The city will decide what tiles it needs next, so if you set the city to emphasize growth, it will try and extend the borders along rivers and plains to get all the fertile land it can. If you set it to production it will try and grab hills and... whatever else has production I guess.
Buying up land (as Sam alluded to) can make the AI upset if it is near their borders. Also the AI will get upset with you if you have a lot of army units marching near their borders and they may ask you to move along a different route.
City states don't just flip straight over to a conquering civ, you can liberate them and re-establish their independence. This of course nets you a diplomatic bonus with them. Trade agreements with city states net you bonuses like +2 food in capital, +1 food in all other cities or something along those lines. It depends on the city state and their placement. I also imagine those numbers aren't finalized.
I noticed the catapult used in the combat demo had 6 lightning bolt icons in the lower left of the screen when selected. I asked about the icons and those are promotions. He couldn't say more than that but the catapult had 6 icons in a row. Maybe they only have one placeholder image for promotions or maybe it was combat 1-6 or whatever the equivalent is for ranged units.
Combat doesn't automatically lead to the destruction of one unit or the other, they can just weaken one another and withdraw. You can swap units in adjacent tiles and there are attack penalties for going across a river/attacking a unit on a hill.
edit: Oh, someone else in my showing asked about console versions like civ rev and the Firaxis guy said civ 5 will be PC only and there aren't any plans for console versions yet.
The graphics are scalable. You can run the game in directx 9 mode and with a lot of animations and what not turned off. They are very aware that a lot of fans play it on their laptops at airports or on old PCs so they want to make sure it runs simplified and everyone has a good framerate/load time. The fog of war look isn't finalized yet but it looks like actual fog instead of grimblack darkness right now.
oh the ruins! Instead of just huts there are also ruins you can discover. They didn't actually explore any of them in the sneak peek I attended but I imagine they will have similar bonuses to the huts.