1) No ads
2) The wealth of FILTERED information you get everyday without browsing any other website
I used to waste so much time on techcrunch, venturebeat, techmeme, slashdot, google news, mashable, engadget and the likes. But, thanks to HN, not anymore. :)
1) The groupthink that arises in certain political/scientific/social debates. I find that the nontech debates here are more uniform and less varied than they are on sites with similar quality.
2) While the site's filtration is good, the fact that its only two lenses are "news" and "jobs" makes the community less flexible and, frequently, less engaging.
It's still easily a top three social news site, though, so I'll resume my lurking and quit being a pest.