It is almost identical to 'Combinator', another WP HN app. No login, posting or replying functionality... which is why I'm writing this from my android phone! I do appreciate the cleaner typography and the links in comment actually work (combinator doesn't fix links). It's good, but not as complete as what is available on Android.
Might just be the screen on my phone (Lumia 920) but the orange seems very flouro compared the screenshots.
Good to see some Windows Phone apps on HN.