biggest problem with core data (imo) was they never ported the data controllers (nsobjectcontroller, nsarraycontroller, nstreecontroller etc) which makes dealing with core data much easier (to say nothing about the lack of bindings as used in appkit)
Take a look at NSFetchedResultsController, it gives you what you want from NSObjectController and NSArrayController, and there aren't really UI widgets on iOS where NSTreeController is appropriate like there are in AppKit.
there might not be any native uis in uikit that need nstreecontroller, but ive done custom uis in appkit that utilized nstreecontroller (think of a diagramming ui with groups and child groups) and would love to have been able to use those in uikit too, with pure data bindings....