Update: None of the below matters anymore as Logitech have finally updated the drivers. Choose your device from this page to download the latest version of Logitech Control Center.
Just a quick update to say I've found a better workaround for the issue with installing the Logitech Control Center. Control (Right mouse button for some)-click the LCC Installer and select “Show Package Contents”.
Then navigate to Contents/Resources/Logitech Control Center.mpkg and double click. This bypasses the operating system version check.
Please note though that the drivers only work in 32-bit mode and there are a few oddities with some devices.
Also note that you'll need to create shortcuts to Spaces and Expose by entering some commands in the "Terminal" program. Namely "ln -s /Applications/Utilities/Expose.app /Applications/Expose.app" and "ln -s /Applications/Utilities/Spaces.app /Applications/Spaces.app" minus the quotes of course!
This information was gleaned from the Logitech forums and most specifically, this thread.
