If you're considering a new venture--whether it's a new product line or an entirely new company--the only way you'll find out if your idea is any good is to try and sell it to someone.
A cell phone in a dog park
When Matt Meeker (cofounder of MeetUp) wanted to see if BarkBox would work, he went to the dog park and asked dog owners if they would subscribe to a monthly surprise box of treats for their dog.
And he didn't stop when dog owners flattered Meeker with a casual "sounds like a great idea" or "I'd buy it." He used the Square application on his Smartphone and asked them to subscribe on the spot. That made people put their money where their mouth was and ferreted out any hollow praise.
Today BarkBox has hundreds of thousands of subscribers and Meeker has Manhattan office space housing dozens of employees. But he didn't start there; he started with a phone in a dog park.
All Meeker had was an idea for a product and the courage to go ask someone to buy it. If they said no, he refined his pitch. If they said maybe, he drew out the questions that were keeping them sitting on the fence. If they whipped out a credit card, he tracked how many people he had to speak to in order to get a yes.
Entrepreneurship is the ability to dream in technicolor while living in reality. Anyone can dream about running a hundred million dollar company, but real entrepreneurs like Meeker have the ability to nurture a vision of what is possible while simultaneously selling what they already have.
The worst thing you can do is ask your friends and family for their feedback on your idea. They will tell you it's great and fill you with a false sense of confidence for fear of hurting your feelings.
Try and sell it and the market will give you feedback that is much more important than your roommate's praise or a 60-page business plan.
Just Ship It
Bill Gates is infamous for having reportedly demanded his team "just ship it" even though he knew there would be bugs in various versions of the Windows operating system. I don't think he gets enough credit-- entrepreneurs ship things, dreamers tinker.
Sure, Gates and his team could have fiddled with his software for years and worked out every last remaining bug, but they knew the market was a much more powerful testing ground than a laboratory.
Even the late Steve Jobs shipped things that were less than what he was dreaming of. Do you think the first version of the iPhone was all he could envision? Of course not. He knew that one day his phone would get thinner with a better camera and a sharper screen, but he also knew that you have to start somewhere and that shipping a good product is better than dreaming about a great one.
Can you damage your reputation by shipping too early? Perhaps, but at least you're an entrepreneur with a reputation to manage rather than a dreamer with an idea. Most customers will forgive a new company that deals with problems forthrightly. If it doesn't work, refund the customer's money; if they are unhappy, make them smile.
If you have a killer business idea, congratulations. Now do what Meeker, Gates and all true entrepreneurs do: find someone willing to buy it.