And the connection of those plates to the rest of your case doesn't seem much beyond the drive's own attachment to side rails or 3.5" drive bay.

No kidding. I share your and Tony's skepticism about the thermal benefit of these. Also, even if the attachment conducted heat to the chassis, I'm doubtful of how much that accomplishes. Lian-Li makes some pluggable drive chassis that are much more heavily heat sinked (they even differentially rate them for 7200, 10K RPM, etc) and they make a big deal about their aluminum cases running cooler, but I don't think that's where it's at. Past a certain point, if you don't move warm air out of the case as needed, all the heatsinks in the world aren't going to help. The case of the noisy PC in my original example always seemed reasonably cool; I pretty much sacrificed any heat-conducting value it had by essentially insulating it with DexDamp and foam. I worked instead on better fans and fan control.

FYI, Enermax has some 80mm case fans with a built-in manual speed control that are around $10 at www.coolerguys.com. I just got the parts need to built another cheap (~$10 in parts) multi-fan thermostat for another PC; not as fancy as that Digital Doc, but $50 cheaper.