Joining is immediate, where some Lemmy instances require manual approval even now.

The main page comes off as more approachable and familiar. They also have a ton of local communities (or “Magazines”) so people can do a lot even without the Federation. I find the Microblog stuff somewhat confusing, I think because it doesn’t have much of a UI built around it so it is less familiar than Mastodon. It is fairly centralized though, in the sense that there aren’t that many kbin instances out there.

Currently kbin is the only one I am aware of.