Hmmm. Just went through this trauma with a client who upgraded to Retina. Easiest workaround I've heard - close PS if you have it open. Find the app in your Applications folder, and Get Info (command-I). You'll see a small checkbox for 'Open in Low Resolution Mode'. Check it. Close everything up and then open PS again, checking with a convenient JPG. Your image is bigger, no fuzz, no fuss.