I got these for my studio. Decent sounding control room, hi-end monitors on heavy, top quality stands. There was no perceived improvement whatsoever using these ISO-pads.
So I brought them home instead. Poor sounding room, cheaper monitors on a wooden shelf, basic home recording setup where I mostly do editing/arranging using headphones. In this scenario the ISO-pads actually did something useful by reducing boomy resonances from the shelf. Obviously the ISO-pads didn't fix my poor sounding room but the sound actually got slightly more focused, less boomy.
My conclusion is that these ISO-pads won't do much in an already good sounding professional environment but depending on the setting they may do something useful in simpler, compromised setups, like home studios, etc. Basically, if you've got a problem with boomy resonances leaking into the surface beneath the speakers the ISO-pads may give you a slight improvement. But if your problems are caused by room resonances, don't waste your money on this, get room treatment instead.