I worked on a similar app [1] and it runs as a standalone web app on the iOS homescreen as well. A couple of things that I love about it:
1. I've done away with a lot of the features the OP has - such
as comments (unless it's Ask HN), time of post and link. This
has made it more lightweight and faster to load on slow mobile
networks in my area.
2. Also, it's only updated twice a day since I actually built
this for myself to stop spending so much time on HN.
3. And since I found myself only reading the front page on my
commute to work, it aggregates all the front page articles into
one nice page instead of opening one article up at a time.
Not to take away from the OP, but would love any feedback on the whole "less is more" approach.
[1] http://hn.dinopost.com/