Personally I think things are starting to become farcical, a DAC comparison is one thing and what we all need. Asking if it can hook up to a tablet or phone in a plug and play method is not the reviewers job, that is down to the person BUYING to check for themselves. I want to get a comparison of sound quality and functionality of features, not whether it works on a iPhone 5 or Sasung Galaxy Tablet.
There are already 10-12 DAC's to be compared and if each is only going to get a 5-10 minute listen then its worthless. Each DAC should be compared to every other, and with a variety of musical styles with a STANDARD playback speaker or headphone with a set playlist.
The more factors you add the to equation the more diluted the results. This should either be a serious comparison/review or be titled "How one person chose to spend his money on D/A conversion" and it should NOT be up to us to lay down demands. A USB DAC comparison should not include what sends the data down the USB cable, if its not plug and play compliant then thats down to the buyer to research IMO.