Tried it. While the interface looks 'nicer' at first glance, it fits far less content on the screen. It also had more of an email-y vibe while Zulip has more a chat-y vibe, which I personally prefer.

Beyond that, Zulip is open source and self-hostable, while Twist is not.

Side note, we have a chat about self-hosting set up on Zulip at https://homelabos.zulipchat.com/ with 85 members and growing. It's been great for new users to be able to come in and catch up on old discussions in a way that isn't possible with non-threaded platforms.