Oh, brother, I am slow. I threw the first code at people.redhat.com a few minutes ago. I have a convenient blog entry to remind me that Paolo Albeni forced the issue of binary API for usbmon on October 8. In the event I thought it would be a couple days of work, starting in two weeks. Six weeks later we've got the first useable patch. The whole thing weights at about 1700 lines of kernel patch and 520 lines of a patch for usbutils. The latter adds usbmon(8) and its man page. Paolo also supplied 193 lines of a patch to libpcap. Unbeknownst to me, it had a support for the text API already.
So it was Happy Thanksgiving and happy hacking.
Meanwhile, Markus was prodding me to work on Xen's PV as I promised two months ago.