I figure, in the last ten years, I've seen several thousand harddrives. Either sold them, used them or serviced them. From best to worst they ranked as follows:
WD Raptor and RE
Quantum Fireball
Maxtor Diamond Max (not the 8 or Fireball 3)
Seagate Barracuda
Samsung T-series
Western Digital Caviar
Hitachi
Fujitsu
Connor
The last four are really close. Connor is now gone, Fujitsu doesn't really factor in the desktop equation anymore, Hitachis are just plain crap and every single corrupt or dead harddrive I've repaired lately (at least one a week) is a Western Digital Caviar.