Impressions from playing so far(at the end of the middle ages playing as the Israelis) and from looking through the Civilopedia. Sorry if some of these things have been repeated earlier in this thread.
-First, there are a few civilopedia glitches that really don't effect life much at all. Hyperlink overflow occurs in a few places, the Merkava Israeli MBT civilopedia graphic is screwed up somehow so that it is a lot bigger than it should be, and there is the minor grammar/spelling messup here and there. All pretty minor things, but I'd figure I'd mention them here. BTW, I really like some of your descriptions for the later units and techs. I anxiously await our technocratic machine gods.
-Not that I'm complaining about lots of money, but for some reason I noticed that I started collecting interest(like Wall Street gives) sometime in the early ancient era. I have no clue what started that, and my only guess was from one of the wonders I had at that point which were Petra and the Pyramids. The civilopedia doesn't mention what it could be.
-Perhaps someone actually from Brazil would make a better agrument for/completely disagree with me, but I understand the modern capital of Brasilia is a fairly new city in that nations history. I'm not sure it should be the civ's very first city and capital.
-Why would anyone in their right mind choose globalism as their government? It has horrible, horrible stats in peace and war time. I see a place for the other new governments but not for this one. Also, it might be a good idea to give govt-specific structures for a few of them to futher give them a special flavor.
-I really like some of the new unit paths you have made, but in particular I love the defensive tower units. The arrow towers already saved my ass in a early war with Brazil. In general, some of the new units you added are very cool including the industrial legions and the early mech from Robocop. And space battleships...drool.
The only messup I noticed offhand was that the modern age turret doesn't upgrade to the laser turret in the future era.
-I think you mentioned earlier that you realize this, but there isn't a whole lot of buildings in the future age. In fact, only the Conquest of Mars and the Weather Control Center(btw, I'm really can't wait to get that. What a cool idea) are the only improvements I noticed.
Overall, I'm really enjoying all the flavor you put into this. It's been a lot of fun overall. I can't wait to see what the expansion adds.