Long but good read on product/market fit.
I dig Superhuman so maybe I am biased.
Here are the 4 points:
1) Segment to find your supporters and paint a picture of your high-expectation customers.
2) Analyze feedback to convert on-the-fence users into fanatics.
3) Build your roadmap by doubling down on what users love and addressing what holds others back.
4) Repeat the process and make the product/market fit score the most important metric.
Read on to get the skinny on each point!