@dsmid: Yup, except the hard-reboot procedure has a 'no power supply' prerequisite, which, well, isn't the case with the device plugged to a computer

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(It's been a long while since I actually checked to verify that fact, but, IIRC, that's still specified in the PW2 user guide).
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EDIT: I was wrong, see further answers below

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For OS X users, diskutil list & diskutil umount are your friend

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