Storyboarding strikes me as an example of another problem; it's very nice, but so poorly documented that it can be unclear how to do anything non-trivial with it. There are also a few deficiencies which require ugly hacks.
I think the award in that category goes to NSIncrementalStore :) I could often guess what I had to do in an overridden method...but in some places, I am still scratching my head.
Part of the reason I don't even use storyboards is because of its lack of good UIView manipulation. I do a lot of things in container views and scrollviews that add UIViews as subviews. For the type of UI I'm looking for, storyboarding really doesn't cut it.
