Failed within first 6 hours.
Pros:
Compact, portable
Cons:
Unreliable, crashes
Summary:
Used this on a new 2012 MacBook Pro with USB 3.0 (after reformatting using Apple's Disk Utility on OS X Lion) and tried to copy/paste two folders containing 1.2TB worth of backup data. After a few hours the drive made it about a third of the way through and then crashed, freezing the copy operation, the drive itself spinning, clicking, and clunking repeatedly.
The dead drive would not eject properly, so I had to manually disconnect it and reboot the system. After the reboot, attempting to connect the drive resulted in the same cycle of spinning/clicking/clunking with no response from the drive.
Returned the drive a day after buying it, and will not make the mistake of trusting Western Digital again.