Introduces the concept of "Public" to threads and posts, this is most relevant for posts though.
In a few words, as both threads and posts can be published or unpublished and posts appear within threads it can be tough to get visibility on what's public and what isn't. The new public View field and filter accounts for this and will give you an accurate idea of if a post is public or not and an explanation as to why.
Possible reasons for a post not being public would be: the thread it's in is unpublished, the post is unpublished, both!
Code is in flux and should not be depended on for consistency. Features are added and removed on a daily basis. Please DO NOT post bug reports in this state. Feature requests and suggestions are more than welcome.