Ive played 2 unfinished games so far.
First game on Cheiftan as Russia;
Started at a nice spot, wheat, horses, fish, dyes, silk, lots of forests and rivers. Huge map setting. Lots of iron depostits nearby. Marathon mode.
Spent many of my first turns scouting the continent and making workers. Fought a LOT Of barbarians the entire game, because there wasnt much else. The continent was HUGE...I mean REALLY HUGE, and there were only 2 city states, France, and England to share it with. On top of that they were basically all hundreds of miles away from me. I expanded up to 4 cities and still only grabbed about a quarter of the habitable land that was available (did I mention my starting continent was huge?)
Did missions for a couple of the city states which mostly consisted of killing barbarians and building a road to one of them. Noticed the easy AI (france and england) were pretty boring. England wanted a pact of secrecy against France, and I managed to sign a research agreement with France.
Played this game for a while, but got kinda bored since it was apparent the only combat that would start would have to be initiated by me, and the AI looked really easy to smash at cheiftan level. I also didnt feel like waiting 20 turns just to move military units to the closest border (England) before declaring war.
Second Game;
Playing as Egypt, Large map, Marathon - Not far into this one and I will likely restart, I like the fast build on wonders but my starting area is really bad. I'm stuck on a peninsula thats mostly desert leading into tundra in one direction, and more desert and a city-state (Florence) leading into the continent (which, after scouting, reveals mostly desert, Aztecs, England, a couple more city states, and the Iroqious which seem to have the only significantly green area on the continent. Continent is about 30% smaller than the one from game 1, so I will probably use the same map settings when I restart.
Overall Impressions;
I love the interface. Its very slick for the typical tasks you spend a lot of time on (building improvements with workers, moving units, etc.) 1UPT is an awesome change and I can't wait to get into some real warfare action.
City-states I think will be interesting and I might actually go for diplomatic victories now, since the inclusion of city-states and how they affect voting should satisfy my bloodthirst for world domination. I'll probably allow both as winning option.
Diplomacy feels like its missing something and I need more information than whats given. Its easy to see a city-states relation to you but not the major civilizations. I have no idea what a Pact of Secrecy actually does mechanics-wise, although it sounds fun. Research pacts are the worst change. Really, I had to give up 600 gold and wait 90 freaking turns to get a RANDOM research? I know this was on Marathon mode but damn...I could research about 3 other techs in that time frame. :lol You should at least be able to pick a target tech. It also means I will be making a lot less trips to the diplomacy screen in Civ V, because I won't be trading for techs. Maybe this was more of a multiplayer balance change?
AI can be kinda dumb. I watched for about 200 turns as a english warrior unit was pinned down by a barbarian trireme. The trireme would shoot the warrior with its ranged attack and the warrior would just fortify and heal the damage the next turn. They were still at it when I quit the game having reached the medieval era too.
Ruins are the new barbarian huts, and its cool to find the natural wonders. I like how you can see your city wonders appear inside the city radius on the map, I guess they can be razed now?
No technical problems on my end. Windows 7 64-bit, 4gb ram, Q6600 2.4ghz processor, gts260 (had a 8800GTX that burned out last month). Running at 1680x1050 with nearly all setting at max and I think 2xAA. Tiny bit of frame drop when zooming out really fast, but I mainly play zoomed it anyways.