the USB audio interface is now singing flawlessly with MAC OS X 10.6.5
it can stream 24/192k audio files with ease.
but remember, if you are using iTunes to play your music, it won't stream at its native sample rate, it depends on the rate that is set in you audio midi setup.
if you want to have your audio files playing at its sampling rate, you need a player software that could "switch" sampling frequency in Mac OS X.
Pure Music, http://www.channld.com/puremusic/index.html
it's non free but demo version is available.
it is basically an add on to iTunes so audio files will be played at its native rate.
it's free and formerly called "AyreWave"
again, it can play your files at its native rate but it still contains some bug .......
i'm using Pure Music at the moment.