The sight radius is nice, but hardly game-breaking. Considering that knight/calvary units are already excellent spotters and can move in and out of a city's range in one turn, the +1 sight is slightly less useful. If that were on the Tercio, it would be a lot better since they don't have that mobility. As for attacking cities, I almost never attack cities with my calvary/melee units unless I can't take the city that turn without doing so. For the amount of damage that horses/melee units take, I don't find it worthwhile to sacrifice their health to do a little bit of damage. That being said, there are many worse UU's(I'm looking at you, Zero), but I wouldn't classify their UU's as 'great' by any stretch of the imagination.