For me (echoing some of what gnosis has stated), the real value that HN brings is the discussion. Frequently, I find the comments, insights, opinions, and tangents elicited by HN submissions to be more interesting and thought-provoking than the submissions themselves. I typically browse through the discussion a good bit before ever clicking through to the article/site which initially drove the discussion. There are plenty of "show-and-tell" mechanisms on the Web. What sets HN apart, in my mind, is the round-table that develops in response to a lot of those submissions.