In the interview, Peter talks about the genesis of the project and various design decisions and he gives an overview of the library structure and the differences between the various collection classes. The whole project is kind of a collaboration between Peter, people at Microsoft who’ve helped launch the whole thing and a community built around Peter’s blog and the PowerCollections forum.
One thing that Peter specifically talks about is the BigList class (see also this post). This is a class with a similar interface to the standard List class, but it’s optimised to work efficiently with large lists, especially for operations like insertions, deletions, copies and concatenations. Peter explains the inner workings of the BigList in detail in the video.
Personally, I’ve been using PowerCollections for a while and I think it’s certainly to be recommended as a well thought through collection library. I’ve also had my problems with parts of the design, but nothing insoluble… plus, PowerCollections is not yet final so some problems have to be expected.