Yeah, Baby Cakes is the only episode I do not like, but due to other reasons, namely I don't care for babies. They're annoying. That, and the fact that the cake twins are not earth ponies bugs me for some reason. And Pound Cake being able to fly so quickly is weird as well. I think it was just done for comedy, but it didn't really follow through for me.
As for the episode that I still like but like the least: Mysterious Mare Do Well for most reasons stated previously. Dash is way to arrogant, and that cliff...I'd be okay if they only used it once, but twice?