I'm happy with 1 UPT for military. Any smaller hexes, or any concessions on stacking would really break the idea and I have enjoyed the tactical side and the look of armies quite a bit more since 1 UPT.
However, I think civilian units should stack. There is no reason for them not to stack and it is super annoying when I can't even buy a missionary in my city because a general is there or vice versa. Also, automated workers are forever less efficient because they can now get in each other's way as they're plotting their courses. I also miss being able to double production speed by doubling workers. I do not think this is OP because it requires you to sacrifice building elsewhere, it just allows you to rush hooking up certain tiles in particular which is a realistic thing for a civ game. Soviets did it all the time in real history. this 1 UPT for workers is like watching government road crews. Takes 'em 3 years to finish the simplest things.