i do not use a vibration dampener.
1)my strings tend to make a dull 'thock' sound with one
2)lose power with one
3)lose feel with one
thus i can't begin to see why i would use one. i do have two in my racquet bag along with several elastic bands though in case i am tempted to try blame my poor play on my lack of a vibration dampener - putting it on makes my game worse tho