I got Old World last month, and it's really driven home how much Civs V and VI suffer from the AI's ineptitude: The combat is 1UPT-based, designed in a reasonably similar fashion to Civ; the major tactical differences are the increased variety of unit classes (ala Civ IV), the lack of innate defensive bombardment in cities (I'd be interested in seeing a mod for Civ V or VI that implemented this), and the lack of automatic healing for cities (they need to perform the "Repair Defenses" project), all of which are good, IMO, but none of which shift the combat-paradigm. What really stands out is the AI's comprehension of the battlefield; rarely does it waste a unit, and it's fairly decent at knowing which enemy units to prioritize attacking; its army-composition is also effective, often besting mine. It's not perfect, but it frequently produces formidable opponents that seem to have half-a-clue what they're doing. What I'm trying to longwindedly say is that it made me realize that a lot of dissatisfaction expressed with the warfare mechanics of V and VI really stems from the AI's poor grasp of them. I think that, but for that flaw, everyone would sing the praises of 1UPT.