We like the form factor, 2-TB size, and ease of use which has led us to standardize on this drive with clients for backup to disk. This is a very affordable and capable drive made better by Western Digital's (WD) decision to dial-back the previously aggressive software that installed using two (2) lettered drives rather than one. Great for online backup to disk (See our 'Backup Hints') Perhaps mine is faulty, or perhaps WD had some inane purpose for this button, but decided to leave it as a vestigial feature. I've never had to use it, and when I've tried, it seems not to do anything.
Another slight annoyance is the existence of a seemingly non-functional power button on the back. Furthermore, if you run the included WD Backup Software, you must then use that software to eject the drive before you can unplug.
The annoyance comes from the fact that you must reload/reinstall this driver every time. In addition, I would not recommend this drive to someone who truly wants to use it as a "portable" drive (ie plug n play between lots of computers) due to the fact that for the drive to run a t full-speed you must load a special driver onto every machine. That said, I've been able to get around 100MB/sec and a max of 320MB/sec with 3.0, thus my belief that WD intended consumers to use 3.0 with this drive.
The 2.0 speeds float around 10MB/sec (despite the fact that 2.0 can handle up to 50MB/sec). For some reason, Western Digital seems to have designed this drive only to be used with USB 3.0. However, that is not to say its always slow. I'm not sure what the spindle speed is, but I would guess it's probably only 5400rpm. To my surprise, the drive is actually kinda slow.
I bought this drive to serve as backup for two computers, and for the use of USB 3.0. Super fast with USB 3.0, but the software impedes the ease of use