I picked up a Yaesu FT-1XD at Ham Radio Outlet in Anaheim, and was having some trouble getting it to work with Chirp under OSX. These notes are mainly for my future self, or anyone Googling for information.
The FT-1XD includes the SCU-19 programming cable, which is just a Prolific PL2303 USB to serial adapter. Yeasu doesn't provide an OSX driver, but you can get one from Prolific.
Here are the steps to get it running: