I haven't heard of anybody trying it. Would you be tying it to an Airport Express? If so, I don't think that the USB connection will work - the best bet with an Airport Express would be an optical digital audio cable (the little analog audio output also has a mini-optical connection hiding in there).

If you were talking about just connecting from the computer to the 990, it'd work just fine on a PC but I don't recall if folks have been able to connect with a Mac or not. I suspect that somebody around here has tried that, at least, and while firmware updates can't be done that way (unless you run something like Boot Camp to get into Windows) I guess it's pretty likely that a Mac would recognize the USB connection as an external audio device.