One would think that such a product cannot have a big impact on the audio. Well, it does. A lot.
Most of the monitors vibration, mostly the low end, gets diminished (stolen) if the studio monitors are placed directly on a hard surface. It's even worse if the monitors are sitting on a lightweight wood surface because the resonant frequency will become a nuisance. Using the pads will definitely improve the sound quality of any kind of monitor, especially in the lows, and it's not like an unwanted amplification (like placing a subwoofer near the room's corner). It just feels clearer, better, more correct.
A very nice thing is that you can place the pads at several angles, depending on your preferences.
So don't think too much. They're really worth it.