The latest rev of the Operating System - Jaguar has been a failure (at least from a Developer's point of view). I'm not a happy camper.
You'll have to explain this; the old Mac APIs were a turd. I'm not sure how they could be failure beyond the fact that they are so new that many developers aren't comfortable with the Cocoa framework. The framework itself is elegant, and the underlying Unix architecture is practically the definition of elegant from a developer's standpoint. I develop for a lot of different platforms, and MacOS X Jaguar is actually very nice if you use the native APIs and POSIX libs (instead of the API bridges like Carbon, which are a bit gross).