Xcode 4.5.2が来てたので、ソフトウェア・アップデート経由でインストールしました。
- Support for iPad mini and iPad with Retina display (4th generation).
- Additional bug fixes and stability improvements.
Included in Xcode 4.5:
- SDKs for OS X 10.8 Mountain Lion and iOS 6.
- Auto Layout now supported on both OS X and iOS.
- New localization workflow can share a single base .xib or .storyboard file for multiple locales.
- OpenGL debugger for iOS analyzes performance and suggests improvements.
- Debugger watchpoints can be set when running on a connected iOS device.
- Objective-C @synthesize command is generated by default when using properties.
- Objective-C adds literal syntax for numbers, arrays, dictionaries, and expressions.
- Xcode 4.5 runs on both OS X Lion and OS X Mountain Lion.
- Enhanced for the MacBook Pro with Retina display.
そういえば、一緒に表示されているSafari 6.0.2はエラーになってインストールできませんでした。