Do you mean setValue:ofProperty:? CBLModel doesn't implement -setValue:forKey:, it just inherits the default one, which I believe will use key-value coding and call through to property setters. (It probably fails for anything not declared as an @property, though.)
-setValue:ofProperty: will update the property whether or not it's also declared as an @property. It doesn't send KVO notifications, though.
—Jens