You can allways recocord from an optic or analog audio output, that makes it the most "compatible" audio device.
You should know that most MiniDiscs only play ATRAC files, Sony has the program to convert from MP3 and WAV to ATRAC and pass this files to the MiniDisc, as long as it has the USB connection. I certanly doubt that you be able to convert from iTunes (M4P) to ATRAC with the regular software.
New MiniDiscs players, MD-HD have the new advantage of working as USB Mass Storage devices, this makes it easy to transfer files from Mac, but i realldy don't know if this means they can play other flie formats natively.
Finally, check Minidisc.org they must have a better answer.