I just finished my first game (8 factions, large map, difficulty gave slight advantages to the AI) and... tremendously underwhelmed. Hopefully this'll be useful for somebody fencing about the Humble Bundle that didn't read the last 55 pages...
The UI feels like it was designed for a tablet interface, and left half-baked. There was no information-- Colonel Mustard wants me to declare war on Miss Scarlet. Eruhm... who are you again? Is she the behemoth on the map waiting to stomp my face in if I agree? Why couldn't I seem to conduct diplomacy from the diplomacy tab; I had to look for one of their cities on the map. Why does it take extra clicks to view my units or city info; there's plenty of room on the interface. And I get that WASD has other uses. But seriously, not even giving the option to adjust those keybinds? A thousand niggling interface problems... (For all its numerous other faults, I want to say that, out of recent 4X games, I liked Endless Space's diplomacy interface best. I think it was ES, at least.)
As posted slightly back, the quotes don't seem to do much for me. In addition to the voiceovers giving each faction additional personality, the addition of actual quotes lended it a bit more gravity, I think.
All the data went away. I liked seeing the charts showing how population and military might changed over time ("Hey, I didn't realize that battle for Pleasantville ended up taking out 3/4ths of their army!"), or seeing how wealth correlated to other factors. Or the timelapse maps of territory. Or, to a lesser extent, something from Civ1-- 'Ptolemy's List of the [greatest, wealthiest, etc] Civilizations in the World' that showed up every once in a while (I think it was called that?). And the holobooks from SMAC ("Everything You Ever Wanted To Know About Organic Superlube (But Were Afraid To Ask)", XD)!
The technology tree being a radial web with leaves was an interesting change. Wish you could zoom out on it, to see the entire thing though. Affinities are a fascinating addition. Unfortunately, something I can't quite pin down just didn't work because I ended up feeling that my units were incredibly constrained and equally useless. Benefits from technology felt less gratifying-- probably due to how units mostly got stronger from affinities, and not tech directly.)
Major new addition-- satellites. Personally not a fan, but I think they work out okay? I don't really like how they're mostly limited time effects though.
This one's more of a series of design decisions: I noticed this in Civ5 and was hoping they reverted this one, but why do they seem intent on trying to penalize you so much for having lots of cities (I remember one epic SMAC game where the Morganites ended up with like 140 cities...). And why are cities built like brick walls in the early and mid-game. I felt like Zapp Brannigan, hurling men at the gates until their kill counter maxed out and shut down.
So yeah. UI felt horrible, didn't feel too connected in general, wars took forever. Looking at some of the recent posts in this thread... yeah, it's Civilization in Space. I probably should've known this walking into it, but it just kind of solidified that I don't really like the direction that Civilization has gone recently.