I have used and am aware of node-mongodb-native (I wrote http://stackoverflow.com/questions/19546561/node-mongodb-err... where we discovered it wrapped and threw away all exceptions in callbacks in the stable production version ), but Mongo (the company) have recommended Mongoose. The language now is vaguer than it was 'you can use it natively if you want, or use Mongoose' http://docs.mongodb.org/ecosystem/drivers/node-js/

Thanks for your excellent explanation and totally understood re: not being able to optimise for relationships on the server.