What customers want

In nearly every failed startup, the real problem was that customers didn't want the product.
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Get a version 1 out as soon as you can. But I decided not to, because that's implicit in making something customers want. The only way to make something customers want is to get a prototype in front of them and refine it based on their reactions.
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In a startup, your initial plans are almost certain to be wrong in some way, and your first priority should be to figure out where. The only way to do that is to try implementing them.

Source: Paul Graham's essay  "How to Start a Startup".