Right now I'm using http://ihackernews.com/ and setting a bookmark for it on my iDevices.

The bookmark icon is very clean and I get all of the functionality of HackerNews.

I've tried a bunch of free apps (not going to pay to read free HN) but was disappointed with all of them. Either they don't look very good or the ones that do, don't refresh to show previous posts so all you get are the first page of highest ranked or first pages of newest posts.