I think performance is under-rated by many developers. There are apps that I use and love that block the main thread too often, apps that are otherwise wonderful. I’m disappointed every time I notice. I sigh at the app.
I couldn't agree more. Performance is absolutely critical to the user experience of an app. It is not premature optimization to ensure an app remains responsive to the user at all times and can handle real-world sized data sets. It is good engineering.