That's the prime indicator from what I've read here. Growth to take over new markets is whole point of most startups. I'll add that Jessica Livingston's answer

That's the prime indicator from what I've read here. Growth to take over new markets is whole point of most startups. I'll add that Jessica Livingston's answer in an interview on main thing differentiating founders' successes vs failures was amount of focus. The failed ones got distracted chasing all sorts of activities or sub-goals that weren't measurably helping them achieve the real ones (esp growth). They were just burning cash. The successful ones constantly tried to do anything they could to make something that would achieve growth they wanted. Users massively adopting the product with or without a lot of revenue depending on the game plan seems to be the prime metric after a certain amount of time has passed.