The units, with capacities up to 320GB, aren't all that special compared to any other drive. However, Buffalo will be offering the drive for nearly the same cost as a standard drive, showing that putting stock encryption onto a drive has very little cost. This is assisted by the fact that large manufacturers like Seagate and Western Digital are making drive encryption in hardware a standard option on newer HDDs. Once a drive is plugged in, all that is really required is a password – cumbersome 3rd-party software isn't required.
I suspect features like this are going to become almost ubiquitous on every home NAS, portable drive and even flash drives in the near future.