I feel you - I recently started a node project on LevelDB and ultimately switched over to an SQL database. The difference though is I went for Postgres 9.3, which has incredible native JSON support, allowing you to slice parts of your JSON data out as a record set, join them against tables, as well as other crazy things like partial indexes on deeply nested JSON values which may or may not be present.

I really think Pg is starting to blow Mongo out of the water.