This unit is of average light-weight plastic build quality. I've had mine for about 6 months and have had no operational issues with it, i.e. it mounts & unmounts drives reliably, and transfers data reliably.

However, on my setup, which is a 2012 Mac Mini 6,2 (2.6Ghz core i7), under both OS X 10.8 and now OS X 10.9, ---> THE UNIT SPINS DOWN ATTACHED DRIVES AFTER ABOUT 10 SECONDS OF IDLE TIME. This is *extremely* annoying if you are trying to use the unit for anything other than large, continuous transfers. I.e. if you need to just browse through a folder of PDFs every now and then, or your database serves up image files from this drive, there is a very annoying delay every time the drive(s) have to spin back up from the excessively-short sleep interval.

I have found no way to disable the 10-second idle sleep interval. Unchecking "put drives to sleep" in Energy Saver pref pane doesn't affect it, nor do any Terminal.app-based command-line solutions. This issue is probably something related to a slight difference in the way USB3 is implemented in the dock & on the Mac Mini, and as such there is probably no way to resolve it.

So, in summary, I find the dock is only useful for mounting drives for period backup & restore purposes -- operations that keep the drive constantly busy, so it doesn't spin down & sleep. This limitation is rather hobbling as it removes about 50% of the usefulness of the device.