The 'Datafy' and 'Nav' protocol interfaces look really interesting.
From what I gather using those along with Clojure 'Spec' allow you to create ad hoc, generalized interfaces as an abstraction layer accessing an infinitely large lazy tree of 'things' (provided these 'things' are data or can hold meta data).
Unfortunately I have yet to see anyone really use it in the way I imagine it can be. I'd like to see a web 'req' var with the ability to drill down through the server-code<->js-code barrier (via the session and connection protocol) all the way down into the dom and the js application state. That would be really, really cool.
Also, I've been building a general purpose app builder (for web apps). This app building process is currently working, but in the future I'll need build a more advanced inspector and a designer. Since my stack is Clojure from server to js I'm wondering if it makes sense to build the inspector on top of that trio of technologies then attach the designer to it.
Someday I'll get to do that! ... I just know it. :)
Edit: for those who wonder what this has to do with REBL... these are the core technologies that REBL is built upon.