Xcode 4.4.1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。といっても、実質App Storeから更新ですけどね。
バージョン 4.4.1 の新機能
This update runs on both OS X Lion and OS X Mountain Lion.Included in Xcode 4.4:
• SDKs for OS X 10.8 Mountain Lion and iOS 5.1.
• Enhanced for the MacBook Pro with Retina display.
• Code completion persists your selections to give more accurate suggestions.
• Objective-C @synthesize command is generated by default when using properties.
• Objective-C adds literal syntax for numbers, arrays, dictionaries, and expressions when developing for OS X.
• Apple LLVM compiler supports additional C++11 features, including lambdas.
• Assistant editor tracks caller or callee for the current selection.
• New localization workflow can share a single base .xib file for multiple locales on OS X.
• Source control can commit individually selected changes.
• ARC migration tool converts both retain/release and garbage collected code.
• Fixes an issue where code completion could fail, requiring the user to delete derived data.
• Additional bug fixes and stability improvements.