Personally, I am really happy with how the game is turning out!
The tech tree's eurekas and civics tree's inpiration system seems to be really interesting, and the way your government is shaped thanks to the civics you unlock and the policies you use will make for very interesting decisions!
Also dead-end techs are back, which means the tech tree is far more flexible for modders than Civ V's
Movement seems confusing, I still haven't quite understood how it works. I've seen that you need to have 2 movement points in order to enter a tile that costs 2 points, but there's still stuff that I haven't understood how it works - rivers and the such.
I hope I can get the hang of it quickly enough once I get to play it.
Barbarians seem to be a MASSIVE pain in the neck this time around. They're a ton of them, and they're strong. I think I'll have to use my initial warrior for defense instead of exploration because of them - otherwise they're scouts will be able to report my city's position willy-nilly.
I'm... a bit disappointed at how the diplomacy screen works - or, more precisely, how leaders' animations are not continuous. You meet the leader, they have their introductory animation, screen fades to black and then they return in a completely different pose. They come to tell you they don't like you, they have their pissed off animation, the screen fades to black and then they return in a completely different pose.
It's weird, it's a bit jarring, and it's something that none of the previous games ever did...