"Many veteran developers have learned their lesson and given up on iCloud’s Core Data syncing entirely. "Ultimately, when we looked at iCloud + Core Data for [our app], it was a total no-go as nothing would have worked," said one best-selling iPhone and Mac developer. "Some issues with iCloud Core Data are theoretically unsolvable (stemming from the fact that you’ve put an object model on top of a distributed data store) and others are just plain bugs in the implementation,"
So can these issues ever be solved? "[Apple’s] approach to the problem was very novel and interesting, and perhaps they will ship a version of it that works – but it functions very differently than typical sync solutions in that there is not a central server hub that maintains the ‘truth in the cloud,’" Pierce told me. "Because of this there is a lot of fragility to the implementation, and I’m not sure it will ever scale well to larger data sets,"