v1.1
For anyone wondering, this will update the ATI Graphics Card drivers, and the "GLEngine" (presumably something to do with OpenGL).
To see what files it installs, run the installer and choose "Show Files" from the "File" menu before clicking the "Install" button.
I don't know why its so hard for Apple to provide even a little bit of information about what they expect us t install.
Apple iMac Software Update
for mid 2007 2.0, 2.4, 2.8GHz 20"/24" iMacs
Version: 1.3