Have used Octal for over two years--been mostly happy with it.

* High-quality reading experience. Appends the title and other helpful info to the message if you want to share something, and provides easy options to share the HN discussion or the original article. The UI also prioritizes reading the discussion first which, let's be honest, many of on HN are known to do. ;)

* It mostly stays in sync with the front page of HN (and you can keep scrolling down, making it easier to read stuff that has fallen off the front page but is still valuable).

* The search function finds what I want about 80% of the time.

* You can log in with your HN account and see account stats, I sometimes see issues with the account stats (recent submissions, karma, etc.) staying up-to-date, but that's not a big deal to me.