4. Windows 7 heaven
By itself, Win 7 is a steady if unspectacular operating system. But because it followed the disaster that was Windows Vista, it seems almost miraculous by comparison. Windows 7 rescued Microsoft's reputation simply by not sucking, and the low key way it was rolled out seemed to indicate a Microsoft that was humbled by the lessons of Vista. Now, people are actually excited by the prospect of the touch-friendly Windows 8. No one would have predicted that three years ago.