Started using MongoDB + Mongoid a few weeks ago. I have no plans to ever use MySQL/PostgreSQL for any projects ever again (unless they have requirements MongoDB can't meet).<p>Prototyping without database migrations is amazing.<p>This video on MongoDB-style schema design was extremely helpful: <a href="http://blip.tv/mongodb/schema-design-with-mongodb-3723187" rel="nofollow">http://blip.tv/mongodb/schema-design-with-mongodb-3723187</a>