Nonetheless, it looks like TypeScript is a viable option even for the latest 1.4 version. In fact, Yeoman now provides an Angular starter (generator-gulp-angular) that gives you the option to use TypeScript as your language of choice.
Here are some resources that I thought were helpful:
Why Java Developers might love TypeScript
A longer version:
As you can have a much better OO experience with TypeScript, I think it will be also quite interesting to use rich domain objects with AngularJS rather than using JSON structures directly when retrieving data from your REST endpoints.
There is a great presentation by Gert Hengeveld from NG-NL 2015.
Convert JSON Structure to TypeScript Classes
If you create TypeScript classes that need to handle JSON, the follow online tool to generate TypeScript interfaces from JSON might be of interest:
TypeScript type definitions
I still need to wrap my head around TypeScript type definitions. They basically bolt on type definition for libraries that are not inherently based on TypeScript. There is a repository for them: