Ask HN: How do you know if you're any good?

I started building a web app a few months ago with zero prior experience in software development. It started as weekend hobby, and now I'm trying to make it into a business. It works, and potential customers like it.

But, I have no reference point for what good code should look like, or how long it should take etc etc. My questions for the group:

In general, how do you know how good you are? Could you come up with say 10 questions that sort the wheat from the chaff? How long does it take to get 'good'? Do people think about it?