Pros : I tried this mold originally with Primo Primer, and the cast pieces did not fuse properly (they had little spikes at the top where the frit settled). After consulting Delphi, I switched to using MR-97 and the pieces turned out beautifully smooth and popped out of the mold easily. I would certainly recommend using MR-97 as the release for this mold even though it costs a good deal more than Primo Primer. The hole in the mold is the perfect size to hang the cast pieces, and cords and thin chain easily fit through it.
Cons : The cast pieces are not particularly heart-shaped (the indent at the top of the hearts is not pronounced enough), which is a disappointment. Also, the "earring" sized cast pieces far too heavy to be worn as earrings, and I personally found the pendant sized cast piece a bit large to wear on a necklace as well (I would certainly call it statement jewelry). Having said that, the earrings made nice pendants and the pendant made a nice ornament to hang in a window.
Other Thoughts : If you are considering using a mold which will make holes, I recommend Delphi's Simple Round Beads Mold instead- it casts 6 pieces instead of 3, and I consider all of the pieces it casts to be wearable sizes for pendants.