It turns out this year there was a Google Summer of Code project to work on the Beagleboard and develop a method of proxying USB through the OTG and HOST ports of the device in order to create a sniffer.
Might be worth looking into for those who are working on USB or reverse engineering a USB device. A commercial sniffer for high-speed devices is not a cheap thing to purchase after all!
It's probably not that handy for people debugging extremely low-level USB issues at the transaction/wire level as it's only really a view of the data going to and from the device - it's basically pcap on the USB port (but works with a Windows host, for those devices with Windows-only drivers). Timing could be an issue as well, in case the proxying does not keep up or can't transfer a packet due to memory restrictions.
Something to consider nonetheless. Project link is here.