[genuine]

Friends! Talking through things with honest people is the best feedback. This doesn't work if you have a lot of supportive rather than honest and blunt people around, so if needed talk to strangers first. Try going to a meetup for something in your area- doesn't have to be the same language- there will be geeks there. Pitch to them. Pitch to everyone you can that you think wouldn't mind. And of course, put your site up on HN and ask for honest feedback, but do that only when you have something that you wouldn't tear apart yourselves.

BTW- only building apps where there is a market need is a surefire way to stifle creativity and lose interest. Start up a project on GitHub for fun that does something cool and do that to get your creative juices flowing. Then don't abandon it. There was a study a few years ago that found that the majority of "successful" free or open source projects have a developer associated with them that only started that one or two free or open source projects (ever).