Product review (5 stars): Does exactly what it's supposed to
It's a very simple product, consisting of two long foam strips with sticker material on the back, two metal brackets with plastic spacers, and some screws.  You probably could fake something up that'd work from your local hardware store, but this is cheap enough that it's probably not worth it, and it does the job exactly as advertised.  I successfully stacked my Whirlpool Duet dryer on top of my washer.  The only very minor issue was that there are three screw holes on each side of the back of one of the appliances, two of which are intended to be used to secure the brackets and one of which is supposed to have a screw in it to hold the appliance together at all times.  Well, either someone at the factory goofed or the Sears guys who installed it goofed, because they put the screws in the holes intended for the brackets.  So I had to move those two screws over into the third holes on each side, then the brackets could attach.  Again, it was a very easy fix, and not a fault of this kit, but rather, the assembly of my appliance, but I figure I'd mention it in case anyone else had any issues.

I don't experience any abnormal vibration or anything else.  The washer and dryer are attached to each other very securely with no issues.