There was some discussion on the cryptography mailing list two years ago (much of it poor quality unfortunately IMO):

http://www.mail-archive.com/cryptography@metzdowd.com/msg09959.html

The thread links are screwed up after the first two messages; skip to:

http://www.mail-archive.com/cryptography@metzdowd.com/msg09966.html

and from there you can follow the Thread right-arrow at the top left.

There was another flurry of messages when the client was released:

http://www.mail-archive.com/cryptography@metzdowd.com/msg10142.html