I used it in my desktop (mac chrome) browser, and it's a better UI than the HN website itself - much less pain from context switching. The biggest issue for me is that it's really hard to read text - mainly because there's too much on the page, and the formatting makes it all unremarkable. Even the comment indentation is unremarkable, and easy to miss.

Improve readability and make comments easier to access (perhaps inline them after the article text), and you've created something amazing.