First impressions of Mastodon:
* Discovery is very difficult. This is the best instance list I’ve found: https://instances.social/list/advanced. It’s probably easier to find people to follow if you join an active server and stick to that.
* It seems like Mastodon got a lot of press in 2017 and a few semi-famous people tried to use it like Twitter, but gave up after a few months. Now it's splintered into a bunch of interest-based communities.