I've been avoiding Magnus for quite a while now. I've been taking the opening level of Liang and Pingala (alternating which goes first). Then I've just been letting promotions stock pile until I can get Reyna's buy districts ability. As of GS, Pingala's crazy good. Should also change the dynamics for food/housing in your core city. Overall, the governors look better balanced as of GS. Armani giving you her city state's luxuries can be huge, as it lets you sell more of your own luxuries. Liang's boost to district construction was already mentioned by @NegativeZero, and her immunity to disaster damage could be great for settling under a high yield volcano. Victor and Moksha will be powerful as soon as the AI gets it's act together. But it's unlikely anything's as good as Pingala's new abilities; not even Magnus. I'm not a fan of governors, but GS looks to be an improvement on the mechanic over RF.