I've always thought the MongoDB database was really good, but has poor drivers for node.js. I've been using node-mongodb-native, and it has basically no documentation. If you want to use a relatively new feature, you have to figure out how to convert from the MongoDB command line syntax in the MongoDB docs, to some syntax that the driver understands (which may sometimes be impossible). If you have poor drivers, even an awesome database won't make up for it.
It also requires way more nesting than it should, in my opinion. It would be nice to have a synchronous connect method so that I don't have to wrap my entire app in a connect callback.
And I don't see why 'collection' should take a callback either, unless you're in strict mode and querying mongo to see if it exists.
Some people have written higher level APIs on top of node-mongodb-native, two that I have seen are mongoose and mongous. I'm still evaluating them to see what their performance characteristics look like.
