What I miss on every HN app I tried is a focus on search. Maybe I'm using HN differently than most people, but I usually look for discussions on topics I'm interested in, instead of reading the top posts on all topics.

For example: I'm an Android developer, so I often browse hacker news by searching for "Android" in topics and comments, to see if there are any interesting discussions.

A great app for my usecase would allow me to search and quickly repeat previous searches right from the startpage.

You could add widgets that jump directly into saved searches.