This is a great item, and a great way to put some more sand in our box. My friends and I had a lot of fun with these over the weekend.
But as a result of doing a bunch, just a few suggestions came up:
At first, I thought they didn't last long enough and was going to recommend that they be extended a bit. But in retrospect, I'm not sure that's really the problem. The real issue is that we have no way to know how much time is left, which would help the potion drinker know when to make more obvious hints. A timer over the potion drinker's head would solve this. But if you guys get really ambitious, and sometimes you do, Charades music that speeds up as time winds down would be even more awesome.
A little less ambitious but a nice touch: make it so that if no one gets the answer everyone hears the "Whump waaa" effect and not just the potion drinker.
But seriously, whoever had this idea deserves a raise. Or at least a cookie.