Believe it or not, its their 60GXPs that have given me problems. As of last night, ive lost 3 out of 4. The trick to diagnosing is sound. The bad ones tend to make a clicking noise when you first turn them on for a few seconds. My first 2 that I had both had this, which at the time I had no frame of reference(for that drive ) to compare it to. When they both died and I had to RMA them, only one of the two I got back had this clicking. That one died last night. In all cases, the drives lasted about 2 months after I received them. If you have one of these drives and are hearing this clicking noise emitting from the drive, I would reccomend at least backing up your data, if not RMAing the drive right then.
Hope that gives you guys some more concrete details.