I was the main author of Circle's frontend (the code is open-source: https://github.com/circleci/frontend).

I went on to build Precursor (https://precursorapp.com), which uses Datascript (https://github.com/tonsky/datascript) to accomplish a lot of the things that Om Next promises. If you haven't tried Datascript, you should really take a look! It does require a bit of work to make datascript transactions trigger re-renders, but the benefits are huge. It's like the difference between using a database and manually managing files on disk for backend code.

My understanding is that Om Next will integrate nicely with Datascript, so you can keep using it once you upgrade.

If you're interested in learning more about building UIs with Datascript, I'm giving a talk on Monday at the datomic/datascript meetup: http://www.meetup.com/sf-datomic-datascript/. I'll be going over Dato (https://github.com/datodev/dato), a framework for building apps like Circle and Precursor.