Last week I got a Valley Enterprises FTDI chipset-based programming cable for my Yaesu FT-817ND. This is a USB version of the Yaesu CT-62 serial cable used for rig control and programming.
I took today off to finish my income taxes and after I was done I decided to play with the cable. I already had an FTDI driver on my MacBook Pro, so I was able to just plug it in, connect it to the radio, and use it to program the rig using CHIRP. I also tried it with Fldigi and once I selected the correct driver in the config screen, it worked. If I put the rig into memory mode and manually selected the frequency it immediately showed up in Fldigi. Likewise, if I used Fldigi to change the frequency it worked on the radio.
Tomorrow I'm planning to head down to Ham Radio Outlet and pick up a Signalink USB, among a few other things. The Easy Digi interface I have now works but it's a rat's nest of cabling. The Signalink USB should reduce the clutter and simplify setup and teardown. Combined with the Valley Enterprises cable I tested today, it should make digital mode operation a lot easier.