I had developed a tremendous amount of diagnostic cruft as I slugged it out with the FUSE/libusb (each had their own unique pound of flesh to collect) and removing it all took a bit more time than I expected. My apologies.
This is a Mac OS X 10.4.8 Intel executable. PPC/Installer etc in the future.
You can look, you can read, no writes yet.
You need to have the Google port of FUSE installed and the libusb as linked in the first post in this thread.
Example of using it in Terminal, with Sony Reader plugged in...
If you get an error about not able to find something, remember you need /usr/local/bin in your PATH to get at FUSE.
I've got a start on a Mac OS X GUI listener application that will listen for the Sony Reader being attached/deetached and bring the filesystem up and down automatically.
I'm working on the bug about ls'ing the dev/fd/10 directory on the Sony Reader. For now I suggest being careful of the /dev directory, ls'ing in there causes the Reader to crash.
If you crash the Reader just umount and then re-run the readerfs after the Sony recovers.