Rich Siegel of Bare Bones Software:
Finally, one of the most maddening issues: the iCloud-just-says-no problem. Sometimes, when initializing the iCloud application subsystem, it will simply return an opaque internal error. When it fails, there’s no option to recover — all you can do is try again (and again…) until it finally works. And when it does initialize successfully, it can take an extremely long time. In some cases, we’ve seen delays of up to 25 minutes while waiting for the iCloud stack to initialize. There’s no discernable consistency or rationale for when it says no and when it finally says yes…you can just keep trying, and eventually it might just work, or not.
Yet another scathing writeup of the shortfalls of iCloud + Core Data.