> Every major competitor to Ember (including its predecessor, SproutCore) has a data layer that does more than pass the buck off to jQuery

SproutCore had a robust data layer, but 2013-era frameworks mostly expose HTTP directly as the abstraction to use, either via $.ajax or a framework-specific HTTP library. Other frameworks are not trying to solve data persistence and loading beyond delegating to HTTP, but Ember's solution isn't ready yet (so we don't get to say that it's a win of using Ember over the competition -- yet).