I've been using RethinkDB for a while now and I really enjoy working with it. It's a great fit for React and Angular 2 apps with their one-way data flow through the application. Hook up a store or a model to an event source (server-sent events) that streams the RethinkDB changes feed and it's just awesome and simple. Realtime shouldn't be this easy, totally feels like cheating. Love it.
I also really like the ability to do joins, where before in Mongo I would have to handle data joins in the app level.
I also really like the ability to do joins, where before in Mongo I would have to handle data joins in the app level.