Reddit opened up a world of computer programming to me back in 2007. I read blogs and books I'd never of heard of otherwise. It expanded my world view. I wish I'd been reading it when I was 14 instead of 25 after I finished university (I scrapped by in a shitty IT degree). I would have focused on maths and programming. It expanded my world view and opened me up to a lot of good influences.
Yeah it has an addictive dark side. Also most of the user comments went to shit years ago. But overall a net win for me.