For me it's before and during. HN is a deadly weapon in the hands of a shrewd business opportunist with kickass hacking team/skills.

It has been an MBA for me.

It's definitely useful in moderation. I think most of us would agree that we find a lot of the comments to be valuable and insightful, as with some of the articles.

Of course, "in moderation" is key here. Spending all day on the site probably isn't a good use one ones time. Popping in for a few minutes throughout the day is probably pretty safe to do.

What have you learned here that you didn't know already?

The transformation from a shrink-wrap industrial software developer to doing web-startups. It takes two different minds; previous projects were hard and very demanding, and they were sold via word of mouth and ads in trade publications. Web business is entirely different.