Biggest problem is the lack of a proper way to update data thru the app. More often than not, we end with a big mess of singleton, notification, badly implemented kvo... and if you're not lucky, you'll have to fight to get an authoritative source for the data, or the latest one. When I see what's possible with solution like Om, I'm very envious (not that it's a silver bullet, but it's a major step forward in my point of view)
You should try Realm. We radically simplified the architecture of our app by using Realm as the authoritative source of data (equivalent to a redux store) and then having all the views reacting to changes in the model. This also allowed us to have all writes happening background threads.
