Not sure if you find it cool because you got an iOS development background but http://epf.io that works with Ember (sorta like a replacement for Ember-data) shares the same semantics that Core Data does with its Context Manager (scratchpad).
You can have child contexts and merge to the parent and so on. Check it out.
Anyone using this in production? I've been looking for a stable alternative to Ember Data for a while that helps you with things like rolling back when the server returns an error response.
This probably seems a little weird - why wouldn't I want to give it a go? I guess it's because I've been using AngularJS for several months now and learning something as opinionated and complex as Ember is a pretty hefty investment in terms of time and effort.
seivan mentioned ObjectController and ArrayController, which I think are really cool. Does anybody else know of any other features that might whet my appetite and convince me to jump on the Ember train?