USB 3 operates at 5 gigabits/sec (like PCI-Express), uses separate transmit
and receive differential pairs, (like PCI-E), data scrambling (like PCI-E),
a link training phase (like PCI-E), and spread-spectrum clocking (like
PCI-E)...One naturally wonders why we couldn't all just use External PCI-E,
so I have to assume the advantage is not going to be found in the electrical
specs.  Probably more to do with the failing of PCI, SATA, and so on, that
you have to reboot the operating system after you change a configuration.
With USB, you just plug it in, and go.  Yet, I think the shortcomings in the
other protocols are in the driver software, and not the protocol.

The opinion of a co-worker is that External PCI won't catch on because it's
way too fast for anything you'd plug into a PC (except for video cards).
And I'd apply that to all the other fast busses.  But, we are engineers, not
marketers :)
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