I'm in the midst of a troubleshooting process, but it appears that when I attach a USB 3.0 device to a hub (which is already plugged into the computer) on my rMBP, if Fusion is running it will not mount (either host or guest, and I've selected connect to host). Even closing Fusion does not allow it to mount (even with a plug/unplug). If I plug it into the other USB port, then it mounts. Only a reboot will allow the devices to mount once they fail to do so.
I haven't fully nailed this down to having Fusion, but it's looking very much like it is a problem. Anyone else seeing this behavior?