I wrote:
Allmydata, Inc. uses Twisted in its current proprietary consumer backup product [1] as well as in its free-software distributed storage grid project [2].
...
Oh, and apropos the discussion about Twisted-on-Windows and iocp reactor, I should mention that the current consumer-usable product [1] runs exclusively on Windows (although the non-GUI, server part of it also runs on our Linux servers). The new free-software project [2] runs on Linux, Mac, Windows, Cygwin. We use the select reactor exclusively. Every couple of months we experiment again with switching to iocp reactor, and we hit a bug that forces us to switch back to the select reactor, e.g. [3]. The good news is that it's a new bug each time... Regards, Zooko [3] http://allmydata.org/trac/tahoe/changeset/524