HN and Slashdot are the exact same site at different stages of life.
They begin as the news site with articles that only about 1000 people care about. So you'll go there because reading every single post on Lambda the Ultimate takes too long and you want a community that does the hard work for you of picking out the wheat from the chaff.
Then, after about three years, articles that compare the performance of subroutine threading vs. switch statements in interpreters slowly disappear and are replaced by articles about how the new Apple product is ingenious because it's the size of most people's thumb. Then comments become shorter, and you realize you no longer read the comments to gain a depth of knowledge. Where before you were continually amazed at some people's insight, now when you ask an honest question you are more likely to be flamed by a nerd with a chip on his shoulder that's desperate to start and win an argument.
For another year or two occasional glimpses of the better articles and comments keep you coming back, but after a while you start to go looking for the next site that's long on interesting and short on raging arrogance.
Then, five years after that, you might go back to the old site to see if it ever changed, and instead marvel at the cesspool it's become.
As a techie, you will have this experience once or twice a decade. Slashdot in its heyday (1997-98) was the HN of its time.