Sites like CocoaDev try to maintain some semblance of a knowledge base, but it's still woefully inadequate.
Apple refuses to publish code snippets, and their API docs consist of little more than what you would learn from the header files.
Mac development is a pain in the ass, even though I like Objective-C as a language :)
The API documentation is better than most development environments I've worked with. Admittedly, Apple's secrecy problem gets in the way of publicly acknowledging bugs, missing features, or planned upcoming features. These things can be frustrating. Apple publishes a large selection of sample code though. In fact, they ship a lot of it with the developer tools themselves (plus all the docs), so you don't always have to go looking through the website.
iPhone development is undeniably worse right now. I imagine this will change over time, but I agree their is a lot of work to be done on that front.