While I’m not planning to immediately switch to Mountain Lion as my main system, I do want to take it for a spin, so I went out and installed a copy that I bought from the App Store. Having read on various websites that the OS X 10.8 installer (InstallESD.dmg) is automatically removed from the computer upon installation, I made sure to make a backup copy first using the Show Package Contents drop-down menu.
Because of limited disk space on my startup drive (which can boot up in either Snow Leopard or Lion), I opted to create a small partition just under 20 gb to host my new Mountain Lion system. The download took about an hour over my wireless network, while the actual installation process took under 30 minutes to complete. After filling in the obligatory setup screens, I rebooted my Mac and took my first peek at the Mountain Lion desktop, whose background image resembles the default graphic found in Lion. I then ran Get Info in a Finder window to determine how much disk storage is used by Mountain Lion. I learned that the installation took up 13 gb of space.