I've noticed that it takes much more social interaction to get the social bar maxed out. I don't know if it's deliberate on the part of EA or if it's a bug, but it's definitely there. I haven't tried potty training yet, but I'll check that right away and see what my toddlers do.
Edit: Potty training was fine. I have triplets and none of them gave me any trouble at all. Candy, what was the mood of your toddler when you had the kicking and screaming. I've had that in the past and it was when the toddler was tired, but when her needs were all green, she did ok.
I've also just noticed that a Virtuoso now gains xylophone skill twice as fast. Scratch that. The toddlers are ghosts and vampires, so that's probably why they are learning it so fast.