I was surprised to see that iOS is beating firefox. While this is just one website, I hadn't realized firefox had dropped so much in the ranks. It's still my browser of choice.
It's not a global sample. It's a sample of HN readers only. That means it's dominated by a population focused on web development, which means it skews heavily OS X and Chrome (and to a lesser extent iOS). Firefox remains popular among the general public, though it's dropping fast in the face of some really great work by Chrome. Obviously IE remeains popular too, and it doesn't even register on the linked chart.