It's up (and fast) for me rn. They have been getting DDOS'd in a way specifically targeted for sites running Lemmy. Lemmy is still beta software so hopefully this can be a growing experience for the greater Fediverse. The .world admins are some of the most capable out there.
Well, a lot of the communities are hosted on world. I know they make the biggest single contribution to my federation ingress. So, I mean you will kinda notice a bit of a content drought if they're down long enough.
lemmy.world is definitely the biggest instance with it’s 126k users, but lemmy.ml with 46k, lemmynsfw with 35k, hexbear with 24k and sh.itjust.works with 22k aren’t small either
Yes, lemmy.world is the biggest, but the next four biggest instances combined have just as many users.