The rubber standoffs are quite hard, and don't do much for vibrations when mounted underneath- they work best on the side of the cooler, as they bend a lot easier than they compress. The Zalman is more about cooling than silencing, and it does a reasonable job with very little airflow. Most people here believe that the soft silicone grommets that Antec include with their cases is the way to go to reduce vibrations- these work a lot better than the Zalman standoffs, but do nothing for the cooling (in fact, I think I remember seeing someone mention that by decoupling the HDD from the case, the temps actually rose, because the case was acting as a heatsink).
By the by, I'm not sure how $20 is "somewhat costly" for someone with a watercooled machine, but never mind...
As I said, the main benefit of the Zalman is the cooling (and to a lesser extent, the cool-factor
). That review is out of date, there is now a newer version
available, with more pipes, and a chrome finish for the pipes as well. I have two of these in my machine, and I combined them with the soft-grommets from the Nexus mounting kit
to get the best of both worlds. Incidentally, this kit comes with fan-mounts for closed-chassis fans as well, i.e. no more dremel'ing your nexus fans!
And yes, HDDs usually have four mounting points on the PCB-side- this is the base, but it cools better with the PCB facing up for some reason.
Hope this helps.