Just to note, SC 3 is out. The Developer's Edition is outselling the Standard Edition by about 10 to 1, which is weird. I doubt that many people want to develop for the game, so why spend more money?
I realized today that Edges are self balancing. If you define the Edge broadly, you cover more conditions. If you define it more tightly, it's more likely to be able to stack with other Edges. I love self-balancing stuff!