Counterintuitive startup insight: complaints are a leading indicator of product-market fit.

Another great description of Product-Market Fit:

• "The product is half-broken, and your customers are still using it."

• “Customers are constantly complaining about your product, but they keep sending you feature requests.”

Another gem from Elad Gil:

"In general, things that work tend to work pretty fast, and usually that's within the first year of launch. Now, 'work' is an interesting word—like, what does 'work' mean? Like how much traction is that? And usually, what it means is that you start to see some reasonable growth rate in terms of adoption and revenue, or just adoption if it's a consumer product.

And usually, when somebody hasn't had product-market fit before and then suddenly they have it, they really can feel it. That's things like the product is half-broken and your customers are still using it, right? It's like Twitter during the Fail Whale days. But it's also all sorts of enterprise software or open-source tools or other things where it's just kind of half-broken, but you're using it, right? That's usually a very good sign.

Or your customers are constantly complaining about your product, but they keep sending you feature requests. You know, or just feature requests—like, how many asks are you getting from your customers in a given moment? And it may feel like, 'Oh my gosh, I haven't built anything, this is awful.' But the reality is, that's great; it means people care.

And so, you kind of want to look for signs that people care. One of the mistakes people make is that they try to build something that's very, very broad upfront, and then nobody cares. And I actually do believe in the sort of YC-ism of focusing on something that a small number of people really love and expanding from there versus trying to please everybody.

But the flip side of it is you need to ensure that you keep expanding that base. And usually, again, that's that product or that market pull. Yeah, and I think—I mean, I definitely agree with it—it's like, you need to have at least a small number of people care about it, but you also have to ensure that a bunch of people don't get stuck there and they actually go from there."