I was reading Paul Krugman's column in today's New York Times in which he  used the abbreviation "O.K." That got me thinking--should it be "O.K." or "OK." (We'll discuss whether I have a life later.) That led to my next question--what  does  Bryan think? Garner's Modern American Usage finds either okay but OK is used more in informal conversations. The Associated Press Stylebook finds OK okay as well but frowns on okay.  Garner does say that the New Yorker likes O.K., so it must be a New York thing. I didn't realize until I opened Garner  that OK is "the most successful Americanism ever--perhaps the best-known word on the planet." (Page 588) I'll treat OK with more respect in the future.