Hmmm ... ignoring my silly profile name, I've been an acoustic consultant and researcher for 27 years, having run my own consultancy for the past 20 years doing plenty of acoustic specification projects and lecturing on building acoustics at University. A big red flag is using the word "soundproof" but I understand it's used unscientifically. That wall system shown at 0:53 would not achieve our (Australia) building code acoustic requirement of Rw+Ctr 50 for walls between Units. "Drum effect" is commonly thought to be from reverberation build-up but that's not correct for low frequencies (ie, the "drum" frequencies in which all partitions perform worst) as cavity dimensions are too small compared to wavelength. The real issue is sympathetic panel resonance because both sides of the wall usually have the same plasterboard (PB) lining and stud spacing is obviously a constant (This is treated in double glazed windows by using panes of different thickness and for recording studios, putting one pane on a slant). The result is almost no sound transmission loss in specific frequencies. Bulk cavity insulation definitely helps improve Rw by about 6 points and impact clips provide varying and questionable improvement for the cost, although they do automatically satisfy our requirements for impact noise reduction. The results shown at 2:30 show 20 dB increase from 39 to 59 in Rw BUT the entire wall has been doubled - there is no way to determine the effect of the clips. In any wall where the ONLY physical addition is impact clips an improvement of 17 dB is impossible. If it WAS possible, I'd certainly be recommending this product in all my projects! It would be good to see an ISO test of a system of PB/stud/insulation/PB/solid clip/furring channel/PB compared with PB/stud/insulation/PB/Mute Clip/furring channel/PB to isolate its effect. As far as the general questionable field of isolation clips goes, I do like this product with its single and minimised fixing points.

you should open a dealer/installer in Italy (Milan)... good potential market full of unserious players, so good potential turnover

How effective are these systems in reducing impact noise, coming from side units with hard floors and no carpets? Think of small children dancing in clogs. That's the main problem a friend of mine has and one I will have when I move.

Imagine if you wanted to mount anything like a shelf to the wall. I think this would make that impossible

Uhhhh, Why not just attach it on the outside walls of your home, or building, instead?!? That way you can retain the indoor square footage? Just a thought.