Ya it is the big damage against people running the undead talisman. I was doing this last night on a stealth death striking guy and could more then 3/4 most people I ran across with one hit. Problem I have been facing is you put these on and cannot mount. In vamp form on my sampire this isn't a issue as it seems to override the form change but on a normal char it doesn't.
I was hitting AI's for 50+ and total damage on a DS was 80+ with the first hit, DS(64) and hit spell.
Just tried that casting Gimlet, it does allow you to mount with the flippers on but does not give the damage bonus...back to the drawing board.