Espionage in Civ V is pretty neat. I like it more for City State manipulation than for stealing tech. Every handful of turns your spies have a chance to give you an opinion boost (rigging the election) or you can try to immediately supplant their currently ally (stage a coup).
Religion is better too because it does more than define who hates who the most like in Civ 4. You can hand pick what bonuses you want it to give as it progresses from a pantheon belief to a full fledged religion.
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