Originally Posted by Dynobot
After all HDMI is "made" for audio and video, unlike USB which has only been adapted to serve the needs for audio, but was made for keyboards, printers, cameras, etc.
I naively posted something along those lines about 2 years ago over at Computer Audiophile, and it was pointed out that the HDMI standard was a camel - a horse designed by a committee - and that audio was a very poor second cousin to video in the design process.
USB, like any other bus technology, is purely for data transfer - your comment about printers and cameras is less relevant than 'does USB2.x have the transfer speed I need for my DAC ?'. Proprietary drivers can be an issue, granted, but many modern DACs use the drivers provided by the operating system. Read the list of 'Applications' HDMI was designed for .....
Also, AFAIK, USB has no support for content protection - HDMI does:
Personally, I cant understand why a data transfer standard has to include something so intrusive, but I guess thats what happens when you ask a committee to design your horse. If the aforementioned gadget can bypass any such restrictions, so much the better. I'll leave the Sound Science guys to thrash out the issues around jitter rates over SPD/IF.