I bought the letter molds a couple of weeks back, and only went to use them for the new year's cake that I was making. I decided to look onto the forums after having a heap of trouble getting the fondant out, and read that everyone was having the same trouble.
I found though (through my wife's fabulous suggestion) that a light smear of vegetable oil in the mold, and then placing the completed letters onto paper napkins (paper towel) worked very well, easy to lift out and there was no oil residue on the letters after leaving them on the napkin. I think in future I would prefer a cutter of some kind, but after spending cash on the molds I was determined to find a solution.
I hope this may help others.