It lets you see the raw underlying packets like IN, OUT, SETUP, DATA0/1, etc. That capability would be most useful for USB device firmware developers who might want to see these packets to track down an issue with the DATA0/1 toggling or something like that which wouldn’t be visible in a higher-level software trace like USBpcap or usbmon.
Also, it lets you sniff USB traffic of a different host machine, e.g. USB communication between a game console and a USB controller.
That is my question as well. I've always been interested on the binary blobs that go to HID moce and keyboards. I wonder if this would make cracking those any easier?
I've had a lot of luck capturing USB packets using a Windows virtual machine and Wireshark on a Linux host. Most recently I've used this to reverse engineer the configuration protocol of the Pulsar X2 v2 Mini gaming mouse.
I've also used this to capture the firmware update flow for the gamepad on a GPD Win 2. A physical sniffer wouldn't be ideal here since the gamepad - while USB - is embedded within the device.
