Honestly, the characteristic system is not that satisfying. It doesn't feel like your sims' parenting influences their lives and leaving them a better/worse adult for it. You have to hard grind it out to get the traits, and at that point it feels like I - me, the player - am doing all the work. it doesn't help that many of the major ways to boost your child's characteristics can be done without parents at all.
Childhood phases almost never happen for me. Neat idea, but they're so rare that I don't really have an opinion on them. I like the teen moodswings, which are much more common. But emotions are so incredibly easy to manipulate in this game. Mess-making would be a cute bit of chaos, if NPC kids didn't do it all the time on public lots, regardless of context.
I'd say the main reason to get this pack is the side content. Journals are a good way to build the Writing skill and control emotions, and it adds a touch of character. The table-setting mechanic is incredibly useful for making sure all your sims sit at the table together. School projects are great. The BB is pretty fun, the CAS isn't bad.