As someone actively rolling their own JavaScript framework (more as a learning exercise than for anything else), I second the opinion that AngularJS is uniquely hard/blackboxed compared to other JavaScript frameworks (which I frequently refer to in order to guide my own efforts).
For instance Backbone is pretty much what would happen (give or take) if all the JavaScript books on how to program OOP and MV* got together and build a JS framework. It's not fancy, it's not "magic", but it is very approachable in terms of advanced standard/best/popular JavaScript programming practices.
AngularJS left all that stuff behind and built their own little world. It might even be a great world, but on the surface or to the implementation-level developer has little to do with "regular" advanced JavaScript programming techniques/patterns.
To me it's a bit like the JavaScript version of Drupal, which gives you a ton out of the box, but is just it's own whole world of conventions etc, that has little do with anything seen outside of itself.