Mac OS X Lion install is done as of today. If you upgrade your system and want to keep the installation file from the AppStore Download make a copy of it before starting the install process. After Lion is installed the huge file downloaded from http://itunes.apple.com/de/app/os-x-lion/id444303913?mt=12 will be deleted.
Warning: there is no Rosetta emulation layer any more – so all PowerPC programs on your system will not be running any more.
… and do plan some time for getting used to the new feature called „natural scrolling“ 🙂