I think it is getting there, people are moving away from MongoDB, towards Riak, but RethinkDB is so much more then Riak and I would rather use it. It is very convenient, it has a panel for trying out queries and monitoring db's, it is fairly easy to setup sync.

I didn't try some big instalation, and I would expect at least some issues, but generally, so far, sun is shining each time I use RethinkDB

RethinkDB and MongoDB, the value is the same.

I think the benefits in terms of programming are roughly the same... but in terms of infrastructure overhead, sane defaults and cost, there's quite a bit of difference.

The programming model is also much much better.

Explicit control over write durability and out-dated reads alone is a pretty big advantage. When you start to factor in how much better ReQL is and the atomic nature of ReQL queries RethinkDB pulls far ahead.

This will probably not be a MongoDB killer. Check out http://www.amisalabs.com. That will have more potential but also probably won't be a Mongodb killer.

Shameful self promotion. However i have to say the SQL and your type system makes me gravitate towards your platform. Can Kill mongoCache for sure