I use RethinkDB in most of my production things. I recommend it.

RethinkDB has been really mindful of its' consistency, has an in the box story for observable collections, and a really great UI out of the box. I really hope I get to use it for more than toying around with.

I'm not sure that I'd choose Mongo over alternatives these days, if I'm on AWS and can use RDS, I'd go PostgreSQL mostly, but RethinkDB, ElasticSearch, C*, and others also have their places.

Agreed, I've had nothing but positive experiences with it.

I started with Mongo too, had some performance issues and started used RethinkDB when they first released it. It does get better with every update.

Same here. It has its quirks, but it works.

Having not used it, I'd be interested to know what those quirks are?

and when I grow big, I will use Cassandra.

I absolutely love Cassandra, assuming you have the right use case for it.

We had some aches and pains with anti-entropy ops back in the day (7TB + on too small a ring) but it's my favorite storage system :)

Mongo in on word: popular. Couchbase, not so much. I'd hazard a bet that you'd find some dirt under that couch if you went looking but not enough people have looked at it yet.

At least you get SQL and JOINs with Couchbase.