The main difference I can see with labels (at least for power users) is that the mails get filtered automatically by Google in these categories. I believe that most of us here on HN won't see this feature as revolutionary but it might help the less tech-savvy ones.
For quite some time, I've been happy with GMail because I set up a system through which each email is ultimately stored in one of my predefined labels. I wrote an article about it [1]. It's both simple to setup and easy to use. And although I don't receive that many emails, I believe it can scale quite easily.