I bought a ITB passport essential several months ago, and I have found 2 possible problems of it.
When it is plugged into my Thinkpad X61, it will make the laptop no responding at all, and the only solution is to restart the pc. After I install the WD Smartware, it is solved. But that software will eat up to 100MB of RAM while running.
I set the sleep timer in the software to be 10 min, but when I try to access folders in the drive after 2 to 3 min, it will take a few second to open a folder, which seems that the disk is in sleep mode.
Next time when I buy another external drive I think I will consider other options.