They're pretty good. The newest ones are quiet even by SilentPCReview's standards, relatively fast, and cheap. Best so far is the SP1614N. (160GB $112)
I own a few. Got a 20GB a few years ago when I was looking for a quiet drive. It's not so quiet anymore but it still works fine. Recently got 3 of the 5400 RPM 120GB drives, one for my ReplayTV and two to hold my ever growing collection of... stuff. They're not the fastest drives (hey, they're only 5400RPM...) but they're really quiet (for now) and Samsung is the only drive manufacturer left that still has a 3 year warranty on their entire line of ATA drives.
They're also some of the most reliable drives around so if you're looking for a drive to throw in a computer you don't want to mess with, you'd probably have a better chance with a Samsung.
Don't know if this has changed at all, but Samsung drives are kind of finicky when they're not the master drive. Other than that I've never heard any really bad things out of the ordinary about them.
I would trust a Samsung over IBM myself.
For those that fought for it, freedom has a taste that the protected will never know. -Unknown Veteran
They don't seem to care what they're paired up with, it looks like the days of IDE drive incompatibility are thankfully long behind us. Of course, with SATA it's not even an issue .