I bought this with a couple of 1Tb Seagate drives, set it up following the user guide and I now have 1 Tb of rock solid (after only a few days admittedly) fully secure RAID 1 storage which can be shared by the whole family including potentially my son at University. The only slight issue during set up was that the software version on the box was well out of date, I guess I got an old box, and the update didn't work the first time, primarily because I lost the network connection during the download/update. Rebooted, did it again and it worked perfectly. For the same price as a single 1tb internal drive a couple of years ago I now have 1Tb Raid 1 NAS, delighted.
I'd like to note that some negative comments about having to access the device over the internet are incorrect, once the initial registration is done you can and should access it locally over your home network. There is no permanent internet link to the box by Netgear or anyone else.