Build one in a month ( http://handlr.sapico.me )
Tag hierarchy/synonyms, votes, rss feed, personal mode, user management, custom functionality based on tags ( eg. Tag personal, html editor, HN comments loading), multiple sites, custom layout based on less, popular and upvoted tags Based on current tag)...
Need to improve search performance though.
Ps. The nice thing about hackernews is the simplicity of items ( a comment is also an item) and the JavaScript/css involved for voting.
http://handlr.sapico.me/Item/Details?id=f187ce8e-2045-e911-9...