Well if what I read on one of the forums (sorry I can't remember which, may have been Tom's) by a person claiming to be a former Seagate employee is true? Seagate suckage makes sense and moreover we now know WHY it happened all of a sudden.
Here is the skinny, according to the insider when Seagate bought Maxtor instead of Seagate making Maxtor better? It brought Seagate down to Maxtor levels. You see Maxtor had these ARM controllers that were dirt cheap to crank out, catch was you had to keep 'em in 5400 RPM drives (and even then they better be well ventilated) because if they got hot 1+1 could equal anything from 1-5 and so the controller would lose its little mind and forget where the end of the drive was and the drive geometry. Of course all the Seagate execs saw was $$$ on how much they'd save on the cost of manufacture so they started using them on ALL Seagate drives and...you know the rest. The reason why you can see a dozen shitty and one good in every batch is that when they run low on the shitty Maxtor chips they will occasionally use some of the more expensive Seagate chips, hence the pearl among the poop.
But after reading that it all made sense, the sudden plummet in quality, why drives below 750GB are good (those chips are based on the old Seagate chips and code) and why we see a good one among the crap, you get lucky on the ARM lotto. It all sadly makes sense, just more short sighted corporate douchebaggery.