Having the SVS Sub feet involved in two systems in my house, I can attest to their efficacy. Also, using Auralex GRAMMA's under my giant bass amp, they work very well, too.
If you were to use both the SVS feet and GRAMMA's in concert, for 1/4 the price of the IsoAcoustics feet, they'd most likely work better in most circumstances. Of course, they won't look as cool.
That being said, I'm not denigrating IsoAcoustics. I use their Aperta stands between my sub stacks and L/R KEF LS50's in my home theater. They do a good, not great job isolating the subs from the LS50's (they weren't actually designed for that). To make them great, I added Sorbothane hemispheres to the top and bottom feet of the Apertas. Problem solved. The LS50's do not vibrate at all from the Rythmik subs below them.
And, yes, I am using SVS Sub footies.
What is not mentioned in the article, though, is that most of the improvement is not with the speaker, but with the floor underneath it. Having your speakers or subs vibrating the crap out of the floor that supports them is much less than optimal. That is why you want to isolate your speakers: it's the floor, dummy!
While my home theater is in a finished basement that has a concrete floor with thick carpeting, I still use the SVS feet because they absorb extraneous vibrations from the sub cabinets. That energy needs to go someplace. Better the feet than back into the cabinets.
When I push the sub stack from it's top sub, the whole stack wobbles a bit. Much like a skyscraper moving in the wind, that ability to dissipate energy is a good thing.
