Mainly, I think it's the actions that have changed the most over the three versions. Those are the ones that the villagers do when they are not actually working. While it can be nuisance sometimes to see a villager wander off to look at the fishies or wash their face, the range of actions has expanded greatly. It's also good fun to watch the kids doing a lot more than they used to. Nursing mothers' actions have increased as well, particularly from VV1, where they only stood around or sat like lumps for two years, "nursing the baby".