I always hoped /r/startups would take off as a complement to Hacker News, but I'm the first to admit this is my #2 destination after reddit (though sometimes its #1). Hacker News is the best kind of distraction because it feels productive. Mmmm... Hacker News...
A lot of reddits fizzle out. There's no mechanism that removes people from a reddit, so it could appear a reddit is lively if you only look at subscriber count.
People post stories, but there's very little discussion.