I use it for (small) production.
Made a custom cygwin install with only the most needed parts of cygwin.
(Be sure to include the sources to comply with licence)
I tested it extensively first.
Made an install and mimiced heavy traffic/inserts/updates/etc.
I use only standard (but complex) SQL though.
Very stable.
Also do the customers have not a single problem for more than a year running
now.
The app is used every day by lots of users.
A win machine crashed, but that's win for you, db was recovered fine.
BUT!! You only have 63 concurrent connections to your database. Win cannot
have more than 65 processes \w the same name,
and 2 are already taken. Every connection has its own process. Win does not
know fork().
This can become a problem quite fast in case of a web application using
non-pooled database connections.
AND!!
as allways you have to know what you're doing, how en why. So there is a
learning curve.
Greetings from Holland, J Hondius