Okay, played around with the drive some more, and my initial disappointment is waning. I'm more pleased with it now.
The drive passed another full series of diagnostics, so there's nothing wrong with it physically. The whine is indeed there.
BUT I don't want to give people the impression that it is anything near loud. It's not.
Having only the hard drive and CPU fan plugged in (through a FanMate turned all the way down), I can make out the whine in a silent room with the case closed. However, you have to sort of concentrate to hear it. In other words, if you're not specifically listening for it, you may not notice it. (I'm sensitive to high-pitched sounds though, so I notice it pretty easily. Still, it's not particularly bothersome.)
Now, with the NMB case fans (regular 12v) plugged in as well, the whine becomes masked by the soft whoosh of the fan noise. Again, if you concentrate, you can still make out the high-pitched whine above the soft airflow noise. But the NMBs become more of an annoyance than the faint whine.
I haven't had the chance to test out the seek noise, but that's not really a major concern of mine. Idle noise is most important to me.
The temp of the hd has varied in the range of 22C to 33C, usually stabilizing around 29 ~ 31C.
Sooo... while I don't agree with Samsung's claim that "you won't even know it's there," it is indeed very quiet. If I had my windows open, I probably would not hear it. I've never had a Seagate, so I can't give any comparisons to any of the 'Cudas, but it's by far the quietest hd I've ever had.
I think the best way to sum it up is this: I'll be picking up one of the 80GB models from Newegg next week.
Hope this has been helpful to some of you still trying to decide on the drive. Now I need to get some sleep!