The Buffalo Linkstations/NAS need user replaceable drives to compete with the likes of Synology and QNAP. I believe Buffalo has the price point to dominate, and the hardware of the Pros has performance meeting or exceeding the competition, but the reality of RMA'ing the whole NAS for a drive failure is not acceptable to many users. Out of warranty it is enough to push consumers to another brand. I understand that there is a way to replace drives, and even info on the forum here to do it, but being unsupported by Buffalo is not a good stance.
