Marco Arment is from my understanding a leading iOS developer, and a paragon of what it means to be an iOS developer (His app, Instapaper, has tasteful design, is easy to use despite offering many features over multiple platforms, it just works, etc). He also releases a lot of information about instapaper which yields insights into the iOS market in general (versions of iOS used, sales by device).

He's become an important tech blogger, too, with several recent front page HN posts (recently, his review of the Kindle Fire). Given his general support for Apple products, this post represents an important shift in his perspective. Maybe its not front-page HN worthy, but you should probably know him.