Finally, CIV5 feels complete. Lots of big changes but also lots of subtle changes, the AI is significantly better!
First off, the game got significantly harder. I've been going from King to Emperor for a while in G&K (King being too easy and Emperor too harsh for me) and with the changes, King is very challenging for me now. It seems the combat got much harder, units seem to do less damage so everything is a bit slower when it comes to combat. The barbarians are ultra annoying too, they pump out units and actually send them at your towns in a constant flow so you actually need to deal with them otherwise they come and rampage. They also seem to make coerced efforts now, I've had groups of 5-6 barbs come at me a couple of times, something I never saw in previous iterations. And it's not just the barbs, the civs are also much better at attacking. They'll actually come at two cities at a time to force you to split your forces and switch their main target when they see an opening, it feels much more human-like now.
The whole trade routes thing is both rewarding and stressful especially at start when they have to move through un-populate territory, the barbs have a lot of fun systematically plundering unprotected routes. The routes also really have a significant impact on diplomacy, helping create a reliable bond with your neighbours without having to constantly give stuff away. I've managed to make very strong bonds with just them, it's really nice and feels more natural than having to give way to unreasonable demands constantly.
As a whole, the AI feels a lot more human. I've noticed that when you are too warlike, all the others will band against you. You can really see trends now with denouncements, war declarations, threats, etc. In older versions it felt kinda random but now it's much better.
I haven't made it all that far yet and didn't play much with the new culture/tourism feature so I can't comment on that.
Overall, it's a very solid expansion. The AI changes alone are very welcomed!!!
Edit: After playing some more, I played a diplomatic and a culture victory and they are very nice changes! And again, the new AI is fantastic, no more psychotic/unpredictable AI, it really feels like global politics now!