It's the most well-balanced of all the game modes and we got it for free. There's little reason to ever not use it in my opinion. It doesn't make the game too easy like other modes can risk doing, and just adds extra features and options. Really great addition. I guess it does neuter barbs a bit, but I think they're too overtuned in the base game so that's fine with me. Really the only minor downside is new city-states in awful locations that get stuck at 1 population for the entire game. But that's pretty minor IMO.