From time to time I need to dump usb traffic under windows, mostly to support hardware under Linux, so my primary goal is to produce dump files for protocol analysis.
For USB traffic, it seems that SniffUsb is the clear winner... It works under XP and has much nicer GUI than earlier versions. It produce huge dump files, but everything is there.
However, my device is in fact usb serial device, so I turned to Portmon which can sniff serial port traffic without USB overhead.
Is there a question in here, or are you just posting what you have found?
If its the latter, this still looks like useful information...
Personally, I'd use qemu or kvm and instrument their USB passthrough code, then use libusb to prototype the replacement driver in userspace (this latter bit I've done before; writing USB device drivers in Python is fun!).
USBSnoop works too - and is free.
Or, you could buy a USB to Ethernet converter and use whatever network sniffer you prefer to see the data.