Never tried that component, but not being able to set a custom font for a text view is such an obvious miss for an OS that claims to be so much text oriented.
I can't count the number of times i've had to bind a UILabel into my code just to set the font.
I know, UIApparence should be the way to set fonts everywhere, but that defeat the purpose of rapid prototyping IB is made for.
There's a third party plugin for Xcode claims to do this called MoarFonts and asked you for $10, however I have not tried that. Runtime attributes patch wouldn't take effect instantly in IB but it works reliably well in our experience.
User defined runtime attributes in IB are great. We use them for font name and other handy things (like CALayer attributes for corner radius, shadows, etc).
A word of caution, though. Using key paths in your categories like "fontName" is pretty dangerous. Apple could add such a property, or your users could already have one on their object, that would cause problems. I would suggest including a prefix or suffix, e.g. "cvs_fontName" similar to three-letter-prefixing.
I'll second the mention about checking the release notes of the latest iOS/Xcode beta, for those who have access. Moarfonts seemed promising, but caused nothing but problems when we tried it.
For anyone building the sample project getting _vImage related compiler errors, link Accelerate.framework.
I can't figure out why that's an issue though — URBImageMediaViewController (dependency where the error comes from)'s sample project doesn't link against Accelerate.framework either, but it builds fine.
There are so much awesome APIs on iOS 7 that we planned to leverage in the future, cutting off legacy platforms simply help us focus on looking ahead instead of backwards.
I know, UIApparence should be the way to set fonts everywhere, but that defeat the purpose of rapid prototyping IB is made for.