I personally have learned quite a bit on HN that has led me to being a better programmer. A discovered Two Scoops of Django (https://django.2scoops.org/), Javascript Allongé (https://leanpub.com/javascript-allonge), and plenty of other things that have expanded my mind. The debate between promises, callbacks, and generators made me think critically about how I do asynchronous JS. The local love of functional programming has inspired me to dive in, and ultimately made me a better imperative programmer as well. And overhype of Edward Snowden's every movement aside, HN does a great job of surfacing stories about the intersection of policy and tech.
I also value a lot of the discourse that happens here. I think HN, even with its flaws, is a better community for discussion than Slashdot, Ars, or most of the rest of the sites covering tech.