Richard Posner is a Reagan appointee and probably the most widely respected federal circuit court judge in the country. His bio is here.
John Roberts, at his confirmation hearing, said that the role of judge is to be an umpire; to call balls and strikes. That is what Posner does, in my judgment. And, here, Posner goes to the extraordinary step of calling out Scalia, his superior, in this article. Yes, Posner has a lifetime appointment too, but this is a rare challenge. You can read it here.