I have done successful RMAs with every drive manufacturer but Samsung and Fujitsu (I just RMA's two drives, didn't come back yet). I have never had to RMA a Samsung drive, but that's not to say they're good (rebadged Maxtor IIRC). And this is the first time with Fujitsu.

As for all the rest, they all have roughly the same response time and they simply replace the busted drive with a new or refurbed one. I have never gotten the same serial number back from anyone.