Yes, I consider it to be a positive use of my time. Here are some benefits:

   - keeping aware of latest tech trends
   - deep deep knowledge in some of the comments about tech stuff and other stuff. I like to learn so this is helpful
   - the ability to shine a spotlight on things I think are interesting, either what I've written (occasionally) or what others have written
   - the monthly jobs post is helpful for keeping an eye on the tech hiring market

You can definitely waste time on HN, just as you can on some of the other sites you mentioned. I occasionally find myself cycling between HN, Twitter, LinkedIn and email, waiting for that hit of dopamine with an interesting comment or reply. When that happens, it's time to go to bed, go for a walk, or read a book.