(That Bat Signal went up...)
I've tried the nobsound springs and the Townshend Seismic Isolation Bars under my speakers and reported on the results in other threads.
The effect of the nobsound was just as the OP described. Opening up of the sound, more transparent sounding mids, highs, lows, speakers disappearing etc.
Ultimately I preferred the speakers without the nobsound springs, just sitting on the carpet over my wood floor. I found the springs altered the tonality just a bit too much, robbing it of some richness, and I also lost much of the "room feel" of the sound - things sounded a bit more like listening to an electrostatic speaker and I prefer more palpable sound.
I thought the Townshend bars might be just the ticket and indeed they changed the tonality less than the nobsound, yet I still preferred my speakers without the Townshend bars (I'm one of the very few apparently). There was just enough of a change of tonality away from what I prefer, plus again there was more "feel" to the sound when it interacted with the floor, more density to the sound.
I'm actually going to try the Isoacoustics Gaia 2 next under my speakers. Pretty late to that party since they've been around and raved about for years. I did indeed buy and test the Isoacoustic pucks for under my turntable (but Townshend springs were much better there).
My hope with the Isoacoustics is that they will sort of split the difference between springs and no footers. Springs so fully decouple the speakers from the floor the sound loses feel and density, but if there is still SOME amount of coupling to the floor but SOME increase in bass tightness/imaging etc, that might be my sweet point. I'll see...