I can't tell you how many times I had people tell me this product wasn't needed. You can do it this way or that way. Or my favorite from an IT Manager: "any IT person worth his ‘salt’ can do it in a couple of minutes". If I listened to these people I would never have created the product, never put it to market and many many companies would be wasting time and money having technicians running around manually configuring wireless cards, when there are more important things for them to do.
These days it is very easy to answer the nay-sayers, I simply tell them how many licenses I have sold and to how many companies across the globe. The proof is in the numbers. They change their tune right away. These are unimaginative people that do not understand innovation and efficiency. In this day and age there are very few things that should be done manually.
They are not all bad people, just people that need to be convinced and shown the proof (beware there are a few bad people that want you to stay small). But what do you do about these people when you are starting out? Well you listen, acknowledge and get your own proof, do your own research, decide for yourself.
By this I mean you have to continue on the path you chose and only change if the numbers don't prove out. You have to base your decisions on actual stats, like number of inquiries and sales. Is there demand in the market? Sometimes you have to see if there will be demand in the market and prepare for it.
You can always listen to friends and people you trust but use your own judgment and be your own advisor. It's your life, your dream, your vision. Make your own decisions.
In short, listen to yourself, but be realistic and look at the facts not opinion.