HN is a fascinating place mainly because it is one of the most diverse communities of incredibly intelligent people on the web.
The level of discourse is usually high while covering a very broad range of subjects. Subject specific communities still exceed HN competency in their respective domains, but nowhere that I've found covers such a diverse range of topics with a relatively high competence.
Unfortunately there are still some very obvious biases regarding certain subjects, but at least the community entertains other points of view.
Although I'm an engineer by training, HN has led me to explore many domains to which I wouldn't otherwise have been exposed. Furthermore, there are some incredible individuals here who I'd never run into otherwise, and discussions with them are extremely satisfying.
Overall a great community, though sometimes limited by the bias of its origins.