I've really enjoyed the Espionage system so far, except for one aspect of it. When you assign one of your Spies to counterspy the mission only lasts a few turns and you have to navigate three different menus just to assign them back to the same location. When you have multiple spies spread out counterspying it can be really annoying to reassign them constantly. Beside that though, I feel as if espionage has found a perfect balance in Civ VI of being useful and engaging both in offense and defense. I thoroughly enjoy capturing enemy spies and ransoming them back.