That's great. I'd love to see you guys completely replace the MongoDBs of the world. Once you eventually reach MongoDB's performance across the important areas, switching would be a no brainer for me, and probably for many others.
RethinkDB CEO here. Don't worry. During early stages of ReQL design I suggested string representation for commands (that start with the dollar sign) and the engineering team kicked me out of the room because that would have opened RethinkDB up to injection attacks. If I suggest something like write durability off by default (or something of the sort) I'll have a full mutiny on my hands.
We're systems people. You won't get another Mongo.
MongoDB has been pretty decent (the defaults early on were probably not the best choices)...
The biggest difference in RethinkDB's approach has been data sanity first, niceties a close second (nice devops and dev interfaces)... It's a very well thought out database, and as long as people are moving a little farther away from SQL thinking and interfaces it makes more sense.
I'm not sure where automatic failover stands wrt RethinkDB, but barring that, I would probably reach for RethinkDB, MongoDB or ElasticSearch for most small-medium db tasks, depending on what the application's needs are. By medium I mean less than 10-15 server cluster. Anything bigger, Cassandra would probably be my first choice.
