I am almost done with unlocking all the technologies on DCity. Just left with the Health ones which I never saw much use for and still don't, to be honest.
Looking at the number of players who have unlocked them, it is the lowest of all the categories and it is easy to see why. They don't bring a lot of benefit compared to the Control or Education stacks.
I'm still waiting for a buyer for the Free Education card that I put on the market. You get a X2 education for universities and that's a huge boost compared to some of the bonuses out there.
Guess most players already have a copy of it and it saves you on buying half the number of universities you would need to get to a 25% technology discovery chance. Well worth the money.