Advertising a half-baked product gets you a half-baked brand.
This is why, wherever possible, we iterate based on feedback, and let our creations market themselves (at least in the first instance).
A distinction worth making: talk is cheap.
Feedback can take the form of words, but — just like with proof of concept — it's more reliable to follow the expenditure of real assets (time, money, reputation etc).
Are people buying more? Are they telling their friends? Are they asking what else you sell?
Only then will you know your product has grown legs.
And from there, it can start running.