Please share your experience with using this product on a PSU?
No problem! I tried one of these out in a family member's PC, it was a generic case and I think it was an Enlight PSU. They had a fanless video card and a passively-cooled P2 processor in there, and the PSU was easily the loudest component in their machine. After installing a PSU grommet I noticed a drop in vibrational noise transmitting through the computer case from the PSU fan. Not a staggering difference, but I did notice it nonetheless (so did they).
I doubt that an accomplished SPCR member would notice much difference from this product with our slower-spinning/less noisy PSU fans (like in a Nexus PSU for instance). However, with a mechanically noisy PSU fan and especially with a highly resonant case, this product does have its uses.
I've not tried the 80mm fan grommet you mentioned, but I did see directron.com carries it. I wonder if anybody around here has ever tried it out? It would be interesting to compare it to our favorite blue foam isolators...