Three keys to building a successful product

1) Your application must save your users significantly more money than any of your competitors

2) Your application must save your users significantly more time in their day-to-day lives than any of your competitors

3) Your application must be significantly more entertaining than any of your competitors

Source: https://medium.com/startup-grind/the-three-keys-to-building-a-successful-app-66dbaf9fcd56#.8g9ta1ik9