Ask HN: Would you consider this productive?

It was just recently that I found about desktime.com. And I was wondering..

Would you consider spending time on HN, CouchSurfing or similar sites productive? I understand that from a boss's perspective, of course not! But, in the long run, and for your own personal growth, it of course is productive. You are learning something most of the time. May be something that one learns here won't be useful right now, but it does have some impact that changes how you act or think later when it comes to using it directly or indirectly.

So, I know that it doesn't counts much to be serious enough. But, would you mark HN or CouchSurfing or similar sites to be productive sites, for your own-self and your growth?

What similar productive/may-be-productive-later sites do you know? ;)