In addition, there's a Info.plist key/value, UIInterfaceOrientation with the value UIInterfaceOrientationLandscapeRight or UIInterfaceOrientationLandscapeLeft, that lets you set the default rotation level and the simulator will start the app in the correct rotation.
EDIT: Also the autorotation only works on ViewControllers. If you only have Views without ViewControllers, (such as the default OpenGL app from the wizard) they will not rotate.