What are the key metrics you use to determine if you've achieved product-market fit?

I like Superhuman's approach a lot and have been applying this for years. https://blog.superhuman.com/how-...

For me, the magic moments are when customers start raving about how the product has improved their lives or work! Seeing high engagement, low churn, and organic referrals are good quantitative signals of PMF. But the qualitative feedback and stories of people loving the product is what really shows you've nailed it!

For me, key metrics include retention rate and customer feedback. If people are consistently using the product and finding value, that's a strong sign of product-market fit!