Are you a multitasker that wants to dabble in two operating systems at one time? On a Mac, that generally means using virtualization software, which is what I do. Currently, Im using Parallels Desktop 4 for Mac, but Im looking to upgrade in the near future. Version 5 launched today and offers some appealing features and performance gains:Full support for Aero in Windows Vista and 7 through Windows WDDM driver, including Aero Flip 3D Virtual machine size automatically optimized for best performan