I love software that does good. Software that nudges towards positive behavior; that is software that takes the fundamentals of a good advice or principles and translates those to serve us well. Because technology should serve us, instead of us serving the technology.
What is the software equivalent to a non fiction self-help book? There are multiple ways to gain knowledge and there are definitely arguments on why books don't work. The answer might be to package good advice into its surrounding software.
The book 'Getting Things Done' by David Allen is a classic bestseller with near-cult following. The book describes ideas on how to manage, arrange, and order all knowledge and information in your life. The ideas in the book are first told through written form but by now live forward through software that is principled by David's ideas. Things 3, Omnifocus or Todoist are all digital manifestations of the GTD method. The apps make less sense if you don't * also * understand concepts from the book like the inbox, someday and projects. The method runs through the veins of these apps.
Being opinionated seems like a prerequisite for building a great product. The spirit that runs through the core can guide the makers. It is this invisible hand that guides a thousand decisions along the way. Without this, the software would feel visionless.
Similarly Superhuman is based on the 'religion' of inbox zero. The advice to keep your inbox to zero is deeply engrained into the core of their service. Superhuman makes email a game, and inbox zero are the clear rules of this game. While I personally don't use Superhuman (30$ per month for an email app seems somewhat outrageous to me) the approach of Inbox Zero speaks to me. I use it as a mental model to treat my inbox as a holy ground. This make me think twice before signing up to something and I hit zero at least once a week. Superhuman even has a functionality which track your 'Inbox Zero Streaks' to build the habit.