Any time I review an app, I compare it to the baseline in the category. When I reviewed Fantastical for iPhone I compared it to apps like Calvetica, Week Calendar, and Agenda. Not only did I find that Fantastical had a better feature set, but it also delivered a smoother user experience. The calendar app category has been around for YEARS, and Fantastical had years to prepare to win. Ultimately as a developer you must aspire to be the best in your category, which often means looking to competing apps and making sure you can outdo them from the get-go — and *don't launch your app until you meet those goals* since any category only has a few real winners. If you can deliver, then you've got a "good idea." You have your work cut out for you.