Even if NoSQL solutions are new, there are no data durability concerns in my opinion.<p>I can talk for Redis but my guess is that's the same for the other datastores. In Redis to have full durability enable append-only-file: it's a text-only file, you can check by hand what's written inside your database.<p>In addition even while running in append only file mode, you can still ask Redis to "BGSAVE" (crete a copy of the dataset into an .rdb file in background). It's a single file and you can save it everywhere.<p>With the append only file, it's trivial to write a script to export ALL YOUR DATA into MySQL every 24 hours for instance. So you have your data in:<p>a) compact .rdb file you can backup easily.
b) the append only file
c) MySQL, where you can perform query to check if the data is sane.<p>In addition in the next months Redis will get a JSON export feature built-in, so you can also d) save data into a JSON file.<p>This new products are still younger than MySQL, and there are more bugs probably, but it's just a matter of being a bit more careful to use this DBs in production without concerns, experiencing a huge performance gain.<p>p.s. since the release of Redis 1.0 no critical bugs were found.