Hi Eric,
Just as a reminder, I don't want to cast this as a boxing match, so hopefully there are no rounds to win or lose -- just trying to keep the idea of implementation being key as the main point.
As you said, sure, maany usb cables would never even work at this length, but that's why not all usb cables are created equal -- likewise for everything else in the chain.
As for the bottom line, my starlight/AP-2/metrum octave setup cost pretty much exactly what a new transporter cost, but what we don't know is how the two setups compare in sound quality, which is really the bottom line.
BTW, the 7 meter usb cable was the most expensive one I ever purchased at $225. I'm going to be evaluating the audioquest carbon next, which is only $118 and right out of the box seems to possibly be poised to step to the head of the pack of the cables I've owned. Even the starlight UltraViolet is noticeably better than the standard issue belkens and monoprice, etc. offerings. So, better design, materials, connectors, etc. does really pay off in usb cable implementation, but what I can't say at this point is where the point of diminishing returns starts. Of course that will be very subjective and system dependent too, so my point will undoubtedly be different from somebody else's.
So, hope you and everybody else is truly taking this in the spirit of providing information, not pushing or bashing any one technology over another. As to what I may use with the BH dac when it comes out, I can't even predict -- I'll try usb (with vaarious cables and such), coax and optical spdif, and whichever sounds best is what will stay Based on what John has told us so far and what I heard at RMAF, I'm betting that the spdif will be the ticket, but I'm also prepared to be surprised. :-)
-- Jim