Safety Function Blocks

Are you comfortable using advanced safety logic that is embedded in a safety system? Having pre-engineered MooN or CEM function blocks can save engineering and testing time, but deviates from the traditional code-intensive approach. If the supplier is IEC 61508 certified, do you have confidence that the advanced safety function blocks work as intended?

This was originally posted in "The Process Automation Usability Project" by the user JoanneSalazar. See the responses she got there and contribute with your own here.