I would stress composability (which fits in with that whole DRY fad). Also, the ability to reason about your code is a big selling point of side-effect free co

I would stress composability (which fits in with that whole DRY fad). Also, the ability to reason about your code is a big selling point of side-effect free code. When you don't have to keep track of a bunch of state in your head, it's much easier to reason about what code does, and find any bugs or unexpected behavior.