I've had a lot of time with the game the last couple days so I thought I'd offer my two cents on it. First, wow. It really lives up to the addictiveness of all civilization games. Like all of them the core is there, the attention to detail, the complexity of both building a stable empire and expanding it, etc. I love the addition of city states as an added wrinkle they give you an incentive to have at least a few states under your protection and give you an extra incentive to go to war and engage with others. The interface is very clean, it runs very smoothly and the graphics are spectacular.
With that said, I do have a few complaints. I think they clearly thought Civ 4 was far too complex, so they wanted to get away from that as much as possible, and while I think they got close to a good balance with this I don't think they quite hit the mark. The inability to trade maps makes absolutely no sense to me. I like not always knowing what the other civilizations are thinking, that's much closer to real life, but no maps? In the real world it'd be pretty hard for any society to travel any distance at all to get somewhere if they didn't have some directions. I would have added a mechanic wherin a traded map is added to the minimap but the fog of war stays the same, that to me would add a good balance.
I also have an issue with the Diplomatic victory. As it stands with every civilization haves 1 vote including city states; there is no scale based on the population and power of civilizations like in civ 4. In theory this is nice, it incentivizes making nice with all of the city states. The problem is if there aren't enough city states left surviving and there are too many civilizations.
In that case you essentially have one option. Destroy more civilizations. That takes away from the point of a diplomatic victory, the victory should come from a proportional vote (I'd say every city has 1 vote, grouped assuming that all of your cities would vote for you of course). This would leave the city states as being crucial influences but also not destroy the balance of ridiculous scenarios where the major powers merely vote for themselves, if they're going to do that there is no point.
I could say more but for the most part I think it's been covered both good and bad.
On the whole, I think this is a fantastic game. I think a couple of patches will make it even better of course as would be expected so I don't blame it in the least. Another point though that I think people aren't really touching on. This was an absolutely needed reboot. Civ 4 was a masterpiece without any question. It was the epitome of what the civilization series should aspire to be. There really wasn't a good way to take that formula and grow it - and make it at all fun for newbies to learn to play it, it would have made it totally unintuitive. Although I think the game as it stands today is a bit too simplistic in some ways (despite it's awesomeness) I see so much room and potential for growth with the new system I'm incredibly optimistic for the series now and going forward.
This game lives up to it's AAA billing but more importantly it gives the series room to grow and expand that just continuing with the formula civ 4 perfected wouldn't have. I'm already imagining an expanded role for city states in future games and giving your "pet" city states technologies and other things to increase your bond and their power. Also, I can see your unhappy cities having a chance to rebel and actually form their OWN city state.
Also, I want city states to form their own loose federations, and I'm NOT just talking about when you get aggressive and start scooping up city states, but actual confederations you can interact with on a diplomatic level to appeal to a group of city states.
I'm sure that everyone has their own ideas to improve on Civ 5's new formula (and i'm not just talking about the currently sub par AI) but I really think the case for improving Civ 4 is much more difficult, and that's the important thing. Civ 4's formula needed to be changed and drastically, and now it's up to the devs to grow Civ 5's formula.