I've done the Alien one and finished it, it was ok. I started the chef one but it bugged and dropped me. I started the Power couple but wandered off. I forgot about the plant sim one, I finished that one and it was ok too. The one I liked best was the mentor to BFF (I think it was). I had a YA raising her younger teenage sister in Mt. Komorebi, it played out a little like a shojo manga, and that game was sweet and fun to play.
So, I've actually done or started more than 4 scenarios.
I dunno, for the most part I find the scenarios to be a little light on play and less like player made challenges than I expected. I like that they're expanding the topic range a little more so there's a better selection to choose from. However, I really dislike the limited time offer thing and wish the Sims teams would quit doing that. I know there are workarounds but I don't want to and more mods makes my game run like poop.