I heard that a particular company, Rangle, worked on AngularJS2 and from what I've heard of them they're an MVP/dev-agency so it isn't surprising to see some of the complaints here about broken backwards compatibility and bad documentation around testing.
Seems few people know how to steward a free/open source software project that has lasted over 5 yrs.
Rangle only created an Angular 2 successor to Batarang. They had nothing to do with core Angular 2 development.
Angular 2 in beta/rc was in many ways rapid iteration on top of experimentation to get the core APIs & developer experience right. They have finally reached a stability point where they feel completely comfortable with the framework they have ended up with as a result, thus the formal release of 2.0.
If you've actually paid attention to the development cycle of Angular 2, it was very fast - it turns out that Google moves much faster than most shops, which was seen in full display during alpha/beta/rc. However, that goes with the territory there, and the versioning did not lie. It is now following semver though, so we shouldn't be hearing of these problems anymore.
Seems few people know how to steward a free/open source software project that has lasted over 5 yrs.