I just took a look, and if I'm getting this right, it looks about as simple as it gets:

SELECT json_data FROM people WHERE json_data->'age' > 15

vs

db.people.find( { age: { $gt: 10 } } )

Personally, I prefer the postgres syntax. It's much clearer. I also don't buy your claims below about performance. Can you provide a real benchmark? Are you running with the safeties off meaning you lose data?