It took me about a minute listening to Peter's system with the Stillpoints on yesterday to realize they are not appropriate for his system - the leading edge was much softer and the bass seriously attenuated. The product has a serious limitation which should theoretically render it inappropriate under speakers, and as Peter says, it is this:
What you want for this application is a solid mechanical ground that also converts vibrations to heat; the Ultra 5s cannot provide a solid mechanical ground, unlike for example, the original single-ball Stillpoints (that I use to suspend my turntable's granite shelf), which is a solid product (no sway, no part movements) and also converts energy. I suspect the Ultra 5s would be more appropriate under sensitive electronics components, but then again, so are the original Stillpoints. Speaking of them, I did compare the original with the Ultra SS's (not the 5s) under the same turntable and heard no apparent difference, some years ago - and they both equally attenuate noise with a simple knuckle rap test.
I suspect solid products like the Magico QPods would be more appropriate under speakers, and I say this simply because I ended up using apparently the same isolation material as Magico - long before the QPods came about - called E.A.R. Isodamp C1002, a product used in aeronautical applications (I believe I had a thread about this product 3-4 years ago???). That product is also very effective under the turntable.
To me, clearly the Ultra 5s are NOT a no-brainer.
This is precisely the conclusion that a fellow a'phile friend came to after putting the Ultra 5's under his Vandy 7's and hearing the same smearing in the leading edge and bass attenuation.