A client recently sought council on some very specific features and benefits of a product under design. Finally, after some prodding, she agreed that what she needed to do was speak directly with prospects instead of spending money on a consultant (sometimes we need to fire customers to help them).
But she was frightened to talk with target prospects and spent several more months making guesses at design and copy. Her product eventually launched but by the time she got to sales and profits she was burned out and hated the process. Her family life and career had suffered. All because she was scared to ask her prospects a few simple questions.
In the end, what makes your project or product successful is getting someone to pay for it and be happy they did so after use.
So before building something, talk to the people you plan on selling to and make sure it's something they want to buy.
In startup circles, this is called Customer Development, and it's critical to launching successfully.