I won't know about this device's reliability for a while yet - I'll update this review if anything goes wrong. Meanwhile, after a week it is giving very good service. The drive slotted right in where my old 300GB Velociraptor used to sit, and looks much the same except for having over three times as much space and being rather faster. HDTune Pro shows transfer rates close to 200MB/sec at the outside, dropping in the usual way to slightly over 100MB/sec at the inside of the disk. Access time is a snappy 7.5 msec.
My two old Velociraptors, bought in 2008, have worked fine for the intervening five years and only recently showed signs of old age. It was Speedfan that first warned me, giving one of the drives zero percent rating for fitness on the grounds of too many bad blocks. HDTune then confirmed that transfer rates had dropped off badly, and one drive actually failed the short self-test. If that happens, you must grit your teeth and replace the failing drive. Wait too long and you could lose data.