In Xcode 4.1 to present (4.2.1), if I close Xcode without first closing the project, the project will be automatically reopened the next time I launch Xcode. Previously I would have gotten the Welcome Screen. Is there a way to change this so that the Welcome Screen is launched instead?
I did not have this trouble after disabling the 'Restore windows when quitting and re-opening apps' in the System Preferences.
System Preferences -> General -> Number of recent items section
Here you can find a checkbox to disable the feature.
However, if you force quit X-code, it will try and launch the projects that were open. Hope this helps.