Pros : Yields good leaf components to use with the other Colour de Verre flower molds. To really use these molds, you need to buy Jayne Persico's book on Glass Kiln Casting. I really only got into these molds after I took a class with Jayne, and she showed us some examples of what you can do with the molds.
Cons : You have to follow the directions carefully. Each mold has specific directions for fill weights that require a digital kitchen scale, and a specific type of primer for the mold (Hot Line Primo primer). To use the mold, you also need to have these other supplies/tools on hand and follow the firing instructions given.