This is indeed interesting! Any googler want to comment how is this different from its cousin Google Closure Library? It looks like it is leaner and more modern. Any other difference?
Closure is a collection of high performance libraries suitable for very large javascript applications and puts emphasis on reduced code size (post-compile) and performance/memory. It doesn't have any HTML bindings so you'd have to do that manually. After compilation I'd argue Closure would be leaner than the equivalent Angular application. I'm sure Angular can scale well, but probably not like Closure. It's no less modern than Angular and still being actively used (G+, schemer).
I'd say 95% of devs are looking for something like Angular. It looks like it will significantly reduce your JS source code; Closure will do the opposite.
There's little overlap between Closure Library and Angular.
Closure Library is a grab bag library full of useful functions that you can pick and choose from and integrate into your own code. Kind of like a standard library.
Angular is a client-side MVC framework that gives you two-way databinding and custom views and dependency injection.
Indeed, in our angular project, we use both - Closure Library for useful functions and advanced compilations, and angular for MVC.