In the audio world there are so many extremes, and different opinions about which is best. In so many reviews one of the steps used to critically listen is to install spikes that are designed specifically couple a speaker to the floor so the cabinet doesn't move around. This product specifically allows the sub to move around without coupling it to the floor. Exact opposites. The real question is does the sub dude come with spikes?
Since the foam in the Sub-Dude's function is to sonically isolate the subwoofer from the floor, my guess is that the foam does not transmit the vibrations that typically cause speakers to move. If the vibrations aren't finding their way through the foam, then the bottom of the Sub-Dude isn't gonna be subjected to any forces that would cause it to move.
Now, when it comes to the subwoofer moving around on top of the Sub-Dude, I don't know, but my subwoofer, which tips the scales at 90 pounds, doesn't seem to exhibit any problems with wandering around my listening area (or, if it does, the distances moved are microscopic).
I defer to someone else's more expert opinion on this latter case, but I'll stick by my guns when talking about the Sub-Dude platform not moving.