I would actually say NONE whatsoever. (unless you have some sort of very specialized DAC that only works well with upconverted files.....but this is...
I easily transfer my music, including FLAC files if I want, to my iPhone and iPad using TuneFusion (a dbpa companion product) and running foobar2000...
hmmm, but why did it work, when I started my project a few weeks ago and all 50 albums showed cover art in the finder? Only from one day to the other...