I'm not sure what you're getting at. Of course your app should be useful, but my point in the post is that that's not enough - you have to think a priori about how to make the app spread.

(I can only speak as a user when it comes to native apps, so what I'm getting at may not align with your point of view or context. Please take my tone not as derision, but pragmatism as a paying customer and interested reader.)

You say "Of course your app should be useful", yet your post opened with "Chances are, someone has already thought of your app idea". So to me your post communicates, "Since your app is just another knockoff, polish it up real nice and hope for a media/celebrity mention or a front page link on HN/Reddit."

My tendency would be to say, "Of course your app should have a decent UI" but having owned a few Android devices and an iPhone, my experience is that utility trumps all. It's not unusual for very useful apps to exhibit truly shameful user experience. They may have a high utility factor and even have a polished interface, but be terrible to actually use. (We're going to assume through all of this that we're not even talking about minimal bugs or smooth, consistent performance, those should also be a given.)

Plus half of your first point was really your second point -- in essence, "Getting People to Use Your App" boils down to "Figure out a strategy to get popular."

Look, all I'm trying to say is that surely, with your background, you have more insight to offer than "...make your app high quality. Hike up production value. Make it really good."

Liiike??