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.