I am afraid http-kit is much feature less than SignalR. SignalR provides client side javascript[1], and hubs. http-kit provide non of these. http-kit just provide a way to get a Channel that can be used to push data to client, The Channel can be WebSocket or HTTP (long polling/streaming). IMO, http-kit is more like a unix command line tool, tiny and focus.
Socket.IO[2] is more like SignalR compare to http-kit.
Yes, it's 2.0.0, that's a promise of the API. No API breaks after 2.0.0 get released (It's already released today).
To tell the truth, I, Peter[1], and a few others take more than a month to think and discuss the API, even though there are just few functions to export. We try our best to make it better. In the end, I think, We are quite happy with what we get now: the unified API.
If a very good idea found to do the API, but the API would break, then it's version 3. But version 2 will still be maintained, and any bugs will get fixed. That's the promise.
pedestal is quite a large project, try to offer a complete solution for building web application in Clojure, from server side to client side, to tooling.
http-kit is a very small and focused library, It just do one thing: talk in HTTP. http-kit need to work together with other libraries like Ring[1] and Compojure[2] to do the server side.
Few good things about http-kit:
1. Very fast and scalable, almost as fast as what you can get from the hardware.
2. Focus, do one thing and do it well, thing about Linux/Unix's philosophy. Personally, I prefer this way of doing software.