MongoDB is very nice. It's basically a bunch of tables with a binary form of JSON they call BSON instead of "rows". You can add an index to an arbitrary JSON "path" and it literally just works. I just wish they had broken out the layers a bit better. You are stuck with their default persistence for example which is very fast but not particularly safe. I'd sacrifice some speed for safer writes on certain collections.

And I am going to repeat the parent's comment that in MongoDB everything "just makes sense". It's just a big bucket with indexes. Everything you need, nothing you don't. So refreshing.