The next best thing to metal molds. Metal types are probably the best but is loosing its popularity due to high cost of production. Polycarbonate molds, without question, is much cheaper and easier to produce. It gives a nice glossy chocolate finish. It is easy to use and easy to clean. Rinse with lukewarm water, dry and use several times every molding session without the need for removing debris. I assume you also know how to use this mold properly or it will be very hard for you.
What about the bad reputation of polycarbonate, the number 7 plastic. It is known to release harmful Bisphenol-A. The very reason why baby feeding bottles were replaced by a more human friendly polypropylene plastic bottles. As for the safety, bispheno-a.org has a well written article about it. Use of polycarbonate products for food applications is very very safe with the migration value of 4,000 time lower than maximum acceptable limit.
update as of June 19, 2016:
Low level BPA exposure is safe according to FDA. See “FDA Approved Number 7 Juice Bottle ?”
There is a food safe symbol (a wine glass and fork) next to embossed 7. I bet a high profile company manufacturing this would not dare putting the mark if it is not true and not FDA approved.
The mold is transparent and has a smooth finish. Looks fragile. I was very careful with it at first to avoid possible break, avoiding collision and drop. However, my care was not enough. And no matter how careful I’ve become, dropping is unavoidable. It has been dropped several times without even a sign chipping. Now, I usually ram it on table to force out chocolate debris.