Cocoatoa: Private API is the Wrong Question.

Rich text editing is made feasible in iPhone OS 3.2 by the addition of CoreText, but just barely. Writing a real text editor atop CoreText is a large amount of work. It is difficult, and painstaking to exactly mimic all the little behaviors that aren’t addressed by CoreText at all.

This is the #1 reason VoodooPad isn't on the iPad yet.