It's been a while since we posted in here and now we're back!
In a nutshell, feedback we gathered thus far on all our USB cleaners is positive. This of course doesn't mean that these products will satisfy every single person out there.
sresener, changes in sound you should look for with USB tweaks are smoothness increase and grain removal, if the so-called musical canvas with all instruments on it is less grainy, these become more easily seen and present, oftentimes bass control improves as well. These changes might require some adjustment time and be perceived as subtle early on, but once our ears are used to them, there's no going back.
It's strange that you didn't hear any improvements, but once in a while a product doesn't meet expectations of a customer and that's fine. Thanks for giving our iPurifier a shot, though!