A professional should develop for his audience - after all, they’re paying for it. But an amateur should develop for himself. It can be a long journey from a good idea to a demo that works. And that’s a journey that you need to make by yourself.
The peanut gallery will pull your good intentions in a multitude of directions. They will offer needs disguised as advice, but be unable to offer attaboys until you have something concrete to show them.
There will be times when life leaves no time for hobbies. There will be times when you want to explore alternate technology. There will be times when the entire endeavor seems pointless. And there may be times when you throw it all in and start anew.
So my advice to Steve Kirks is to write your mac app for yourself. Plenty of time to go public once you have something to go public with.