OK, I don’t know if I’m stupid (if I were, would I know it?) so we’ll just say I am. Regardless, I just received an email with an xlsx attachment created with MS Excel 2007. I’m unable to open it with Excel 2003. I simply get an error stating that “This file is not in a recognizable format.”

Please tell me Microsoft isn’t going to make everyone upgrade to Office ‘07 to view files from their more Office-ly advanced brothers. Those jerks. Of course, you don’t get to their monopolistic status without pushing the little guys around.