What are the main differences between MongoDB and RethinkDB? Things that you hear people care about? I don't use Mongo but I've seen projects that use it. I ask because I want to store & retrieve some analytics.
After seeing the screencast of RethinkDB it seems to me that it's just like Mongo but a much better API and easier handling of sharding and replication. The only con I see of using RethinkDB is that it's very new (so is Mongo...) and probably is little too early for production. Basically I hope not to find worse surprises down the road than I hear of Mongo :P
We're going to publish some comparisons in a few days, but basically you nailed it (both pros and con). We're trying to build a stellar data-oriented development environment/query language, and a stellar scalability infrastructure. All the main pieces are there, and Rethink is a lot of fun to use. The rough edges will be polished out in over the next few months.