Nothing beat being able to test an idea quickly. I now use one tool in front of that process, quick, painless FEA software called Scan and Solve that runs inside Rhino. Able to quickly expose the weak areas in a design before machining, really is an advantage to see where the stress areas are in a part and adjust accordingly.
The classic way to do this was to machine clear acrylic parts and look at the stresses in parts between two polarized filters.
The main thing I have learned from the product to consumer chain is to listen to what the customer wants something to do, not what he or she thinks the product should be.