Just wanted to mention that former Bell Labs staff member Amit Singh
was interviewed on IT Conversations' Technometria program recently.
An MP3 download of the interview is available at:

http://www.itconversations.com/shows/detail1804.html

The topic at hand is obviously Mac OS X internals but, somewhat
relevant to the members of this list, Amit also talks about FUSE and
even name drops Plan 9 while mentioning OSs that have already
implemented userspace filesystems.

For those who wish to skip past the OS X centric portions of the
talk, the talk about FUSE begins around minute 49.