Uninstalling Xcode 4.3
You uninstall Xcode 4.3 like you would uninstall most Mac applications, by moving it to the Trash. Xcode 4.3 is bundled as a single application so there's no need for an uninstall script.
Maurizio Zilli:
"In new Xcode 4 and Lion You can install and uninstall from Preferences : downloads : components
If You want to uninstall completely XCode go to launchpad and push Xcode icon for two seconds, so click on the upper left checkbox."
https://discussions.apple.com/thread/3784638?start=0&tstart=0
To uninstall xcode 4.3.x simply drag the Xcode.app to the trash. That's all.