We started Braid internally in the pre-Slack days (we were using HipChat then), because we felt that "chatrooms" didn't promote good async team workflows. They would lead to a lot of FOMO and constant checking, because if you didn't participate in a conversation at the right time, the topic in a channel would have moved on to something else. We liked the async nature of email more, but, email has it's own baggage.
Our team has been using Braid internally for several years and we're very happy with it. But, compared to Slack, it's best thought of as a prototype / experiment / UI-proof-of-concept, because we don't have the polish and maturity of features that Slack has.
We've had interest from some individuals who "get it", but it's often been hard for those individuals to convert the rest of their teams. If any team here is interested in the Braid concept and wants to give it a serious go, I'm at your disposal, and I'd love to get your feedback so we can keep morphing the product.
The use of "hashtags" in our demos is a bit overdone compared to what happens in practice. It makes it seem like twitter #hastags, but, it's really more like Gmail labels. Braid tags serve the same purpose as Slack's channels, except a given thread can exist in multiple channels (ie. go to multiple teams / individuals) and tags can be added over time (ie. more people can be invited to the conversation).