For many of the stocks I buy, I am guessing it will be useful. I think it is about the many thinly traded on-exchange companies in the 100m to 3B range, not liquid penny stock day trader favorites that trade with penny spreads.
Dude there's way more than just penny stocks that trade with penny spreads. I don't see how this would be useful to anyone and I'm still trying to grok their actual argument for doing it.