Gabriel, here are some ideas for you how you measure your idea.<p>One approach is to list your assumptions (e.g. why does Evernote suck, why would they rather use your app versus writing on paper, they are willing to pay for it, etc). Find customers of your competitors (Evernote, paper-pencil), and validate those assumptions (or reject).<p>Another method you could try would be to create a landing page on <a href="http://unbounce.com/" rel="nofollow">http://unbounce.com/</a> and start pimping that page and collect email addresses. You can also buy some Google Ads for "Evernote sucks". Once you get those email addresses don't get excited about build an app... that'll just be your initial list of customers to interview.