I am a mod on an instance there. Liked at the beginning of the trend, but it has some real problems, so many little irks that makes the real replacement for Twitter horrible.

1. Proper search. I want to search everything that is on the fediverse. Or at least for content that is federated.... Obviously not possible, but this is a big issue already.

2. You can't see followers outside of your instance! Really, try to see who is your friend following/followed and it will show just your instance folks.

3. Do people realize each instance will show different likes/share and comments, as each one is federated with different instances? This is totally nutz in practice.

4. You open a profile and can't see the posts.... because no one from the instance followed that person before and no relay with it... Again, nutz!

And in practice... The problem lies on the lack of quotes, and lack of important companies/news sites/person. I use Twitter to follow some news, see journalists' posts, and that's just impossible with Mastodon.