RE: DF should I be asking you about this?
It is compatible, as I use it. However.... There are a few "non-compatibilities".
A lot depends on how you fly the DF734. If you, like me, start with a cold-dark cockpit, and follow the checklists from the DF manuals, then you will have an incompatibility.
A lot of the checklist calls are missing from FDC, and some of them are in other parts of the sequence. I.E. APU start, APU online, Temperature and Air temperature are missing from the FDC Prestart checklist (those are just off the top of my head, but there are more).
Other quirks I have found are the virtual copilot. There's an experience... Tried a DF flight with it on, and ended up wrestling with the copilot for the flap calls. He'd set the flaps when I didn't want them, I would reset them, he would set them....It was actually quite comical, and the whole time, I've got two voices (DF Copilot and FDC copilot) making the calls. Something to do with DF FMC setting flaps by weight (according to Load Manager) and FDC using set speeds (which you have to change in the options)
Now, don't get me wrong. FDC is an EXCELLENT program, and I love it, but like any good thing, you have to take it's good and bad things, and find a compromise. I tried mixing and matching wav files and file names to work things into the right order, and it works good, but unfortunately, then your stuck with one voice (unless you change all 15 sets), and a non-standard voiceset.
Hope this gives you some insight, and if you fly a lot of the default planes (without extensive panels and start-up procedures) FDC is great. You can also make your own checklists, but, you are still limited to the calls and order they are hard coded as.
Unfortuntely, Dave March has stated he won't be recording anymore calls for the voice sets, and he may or may not release a patch/utility to move the calls between checklists.