I loathe the look of Courier--don't ask me why, I just do. But do I know how the game is played and, more than that, I don't want to piss off the editor and the copyeditor, who are my Friends, I compose in Palatino and, before I submit the ms., change it over to Courier. The whole point of manuscript format is to make your writing as easy to access as possible so that the editor and copyeditor and all other divers hands can do what they need to with it, the better to print it up and sell millions of copies.