The improvements include the ability to download and install Windows 8 Developer Preview from inside the Parallels Wizard, installing OS X Lion using the version of Lion downloaded from the Mac App Store, support for Ubuntu 11.10, an improved full screen experience, improved support for non-English keyboard layouts, and improved migration of recent Linux versions from a PC to a virtual machine on your Mac.
Current users can update Parallels by checking for updates from the Parallels Desktop menu.