Yep, all sim behavior is exactly the same except for a few random differences. A supposedly mean sim still acts exactly the same as a cheerful sim, but they will randomly say some "mean things". My genius/snob sim will run around in the rain like a doofus as much as my playful/loves the outdoors sim. It would definitely be nice to see major differences between sims.
I'm currently playing a sim with the "loves outdoors" trait. It's basically a useless trait imo. He doesn't actually do anything outdoors. He will get on the computer, read books and watch TV all day even when getting the stressed moodlet. I want to see him go outside and cloudgaze, go fishing or do something, anything outside.
Same with the "outgoing" trait. When people come over to the house to visit, the sim will read books, get on the computer or watch TV. These sims should be going out of their way to engage in conversation with guests. Nope, same behavior as every other sim.
Don't get me wrong, I still think the game is pretty amazing and I enjoy playing the heck out of it, but I definitely want to see improvements to individualized sim behavior in future iterations of the game.