It's a fan controller rather than a specific hard drive cooler. It has temperature sensors which'll let you know how hot stuff is so you could put one on your HD and have a controlled fan next to it. If the HD seems to be getting hot you could crank the fan RPM up. Not *really* useful in my eyes. You can get basic rheostats for about £4 whihc allow you to slow your fans to make them nice and quiet. Hard disks are designed to run without any special cooling other than the passive cooling from their bodies. Any fan, no matter how small or low the RPM, is going to help out loads making the drive cooler.
Of course, you'll be looking for something that looks neat on the front of your box with lots of buttons and stuff and the hardcano certainly fits this requirement, so go ahead. Personally I've not used one, I used a Coolermaster Musketeer which only has one fan controller & heat sensor, but has analogue blue dials which I prefer.
Hope this helps.