Ahh, this expansion is more fun than I thought it would be!
I've played for about 3 hours as the Celts, standard pangaea on king, against all new civs but the Dutch. Celts mostly because I liked the UU and UA, and wanted to try religions. Sure enough, I was the first to a pantheon, and thus far nobody else has founded a religion. I really like the variability in religions - I don't see them being irrelevant in any game, and the fact that they have an actual impact on the game (diplomatic, CS, as well as straight bonuses) are all very good things.
Peacetime is more interesting, what with the massive amount of CS quests. The extra quests, in particular, is incredibly refreshing; now trying to ally with City-States is actually fun, and they only ask you to bully other CS's sometimes, not take them out.
I was amazed by the amount of luxuries and other resources on the map. I can't even see iron yet, and the map seems filled! There will certainly be no problems with expansion later on in the game.
At first I thought I'd be spear-rushing Austria, but the game was just too fun to devote all of my effort towards killing a civ early. Then Attila declared on me (which actually was surprising, because Carthage was closer to him) and got all of his rams destroyed by me super-spearmen; I moved up with 6 pictish warriors, but taking his cities is much harder that I thought it'd be.
Yeah, so anyway, I haven't explored every option, or even most options, that were included in the expansion; but it is already shaping up to be a great improvement to the game. Very glad I bought it.
Does anybody else like the mainscreen music for the expansion better than the original theme?