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.
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.
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:
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.
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.
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.s. since the release of Redis 1.0 no critical bugs were found.