I've used Twist, and I've had friends use it in their companies. I know of nobody that continues to use it today.

In my experience, Twist doesn't get notifications or channels quite right. I haven't used it recently, but I think it was easy to miss discussions.

I'm attempting to solve this issue in Booklet by building a deep email integration. I've talked a lot about the summary email. But, one little feature I haven't discussed much is the following mechanism on threads. When subscribed to a thread, all replies trigger emails, and the emails thread in your inbox like a Google Group. (Post via email is on my to-do list, too). My vision is that people can continue to use Booklet from their email (and, perhaps other tools in the future) without needing to log in to the app.