I'm running VMWare Fusion 5.0.3 on Mountain Lion 10.8.5. I'm running as guest Ubuntu 12.10. I plugged in my shiny new 4TB Seagate Backup Plus USB 3 disk in. "lsusb" shows the device, but "fdisk -l" does not show it.
I followed your advice and shut down the guest, and checked the box "USB Compatibility: USB 3.0" under "Advanced USB Options", and now it automounts and works fine! Thank you.