It was insanely great, the computer for the rest of us, and out to change the world. The Apple Macintosh marks its twentieth birthday this week, and--hubris and hype aside--the Mac has made an acknowledged impact on personal computing. A graphical user interface manipulated via mouse, new usability standards, still-evolving multimedia support, and simply cool design are among the Mac's credits, say industry observers, PC users, and Apple pioneers. PC World asked many longtime industry players, including some involved in the Mac's early days, what the Macintosh has taught the PC--and, essentially, the computing industry. And, on the flip side, what has the PC taught the Macintosh? Read more: PC World.