I would call it experienced, same as me.
Where I work, someone had the bright idea that since you could stuff arbitrary data in mongo (for example multi dimensional arrays) that it should be the proper way of doing it.
So now I'm stuck untangling a website that manages millions of pieces of data in about 860 documents or so...
There are also various interesting issues that happen if you have a collection that start with _
Its only possible to edit it through the api, and not the command line mongo shell. The bug was open about 3 years ago and has yet to be addressed. Things like that make me feel that there is still a lack of maturity where it counts.