By the time a NoSQL "database" is ready for prime-time, it will have all the features of a real database.
http://news.ycombinator.com/item?id=3202081
http://news.ycombinator.com/item?id=3982142
http://news.ycombinator.com/item?id=3954596
Real databases have real features like transactions, and guaranteed writes to disk, and not retarded security. Crazy shit like a commonly-used query language and tool support.
If they aren't "prime time" I don't know what is.