There was one reason I used Safari rather than Firefox, and it has recently evaporated. I read a lot of PDF files (>20 per day browsing papers etc) so I was tired of the extra files accumulating in my download folder. You may know that Safari uses Appe’s PDFkit to display PDF files in your browser window, no muss no fuss. Until recently, the options in Firefox were the Adobe plugin (slow) or a privately developed solution tht requires an Intel machine. Enter a fantastic add-on, available at firefox-mac-pdf – Google Code.