Make sure you are wet enough when you put it in so it DISSOLVES completely. Make sure you wait the minimum amount of time or a little longer. I once ended up with "crumbs" because I didn't wait long enough, per the directions. Otherwise AWESOME and have had no reactions.
Pros: Fast, small, easy, clean, discreet
Cons: Sometimes a little bit of a wait time
Bottom Line: I would recommend to a friend