The documentation found here:
http://api.mongodb.org/python/current/tools.html#alternative-drivers
and
https://github.com/mongodb/mongo-python-driver/blob/master/doc/tools.rst
currently says this:

TxMongo is an asynchronous Python driver for MongoDB, although it is not currently recommended for production use.

The link is outdated, but still redirects correctly to Twisted's org on github. It should be updated and the text corrected to read:

TxMongo is an asynchronous Twisted Python driver for MongoDB.

New URL: https://github.com/twisted/txmongo
It is in production use.

The same for here:
http://api.mongodb.org/python/current/faq.html?highlight=txmongo

For Twisted, see TxMongo. Compared to PyMongo, TxMongo is less stable, lacks features, and is less actively maintained.

This is also incorrect, as noted above the URL needs to be corrected and should read:

For Twisted, see TxMongo. Compared to PyMongo, TxMongo is its asynchronous twin. Its stated mission is to keep feature parity with PyMongo.

TxMongo's is actively maintained[1], with corporate backing[2], was absorbed into Twisted's github organization[3], stable[4] and in production use[5][6].

[1] https://txmongo.readthedocs.org/en/latest/status.html
[2] https://github.com/twisted/txmongo/blob/master/docs/source/AUTHORS.rst
[3] https://github.com/twisted/txmongo
[4] https://pypi.python.org/pypi/txmongo
[5] http://www.amplidata.com/
[6] http://www.hgst.com/products/systems/object-storage-servers/hgst-active-archive-system