I was able to get some remote maintenance time on some servers. I never used the USB DirectPath pass-through before so hopefully I don't restate obvious things about the original functionality of this.
1. USB 2.0 hard drive successfully passed through and achived a sustained 100+MBytes/s through the duration of a 4GB file.
2. The pass through was attempted on several hosts. Some required a reboot before I could use the USB controller directly, some didn't (I don't know what the difference once). The one that didn't was a Cisco C220 M3 and had no devices connected, but the port on that server that had something connected required a reboot. Post the reboot the C220 M3 with the hard drive still had the indication a reboot was required but it worked fine. The HP DL360 G7 that I tested last night with the sound card required a reboot.
3. The PCI Device could not be altered while the guest was on (I'm pretty sure this is how it was).
Things I could not test due to being remote or simply forgot until I couldn't test further:
1. Disconnecting and reconnecting the USB device to verify it reconnects properly. If I remember, I will post about this the next time someone is on-site at the NOC.
2. Adding a passthrough PCI device with the virtual machine on. I will test this today or tomorrow when I have a maintenance window on another server with a USB device hooked up.