Saw this tip in the recent NSHipster, which I think is good idea although it's crying out for a nicer syntax:
Passing strings as key paths is strictly worse than using properties directly, as any typo or misspelling won't be caught by the compiler, and will cause things to not work.
A clever workaround to this is to use NSStringFromSelector and a @selector literal value: NSStringFromSelector(@selector(isFinished))
I'm suggesting that the syntax @|isFinished| would fit nicely into eero. Forgive me if this is already in the language.
Also, even though there may be less call for using NSStringFromProtocol, why not use similar syntax on protocol literals, even if only for completeness?