I am getting ready to install XCode 4. First, I wanted to uninstall XCode 3.2. Here are the steps.
Open a terminal window.
Change to the root directory:
Uninstall all of XCode:
sudo Developer/Library/uninstall-devtools –mode=all
It takes a while to uninstall everything. The uninstaller seems to leave behind the documentation files under /Developer/Platforms/iPhoneOS.platform folder.