https://developer.apple.com/library/ios/#documentation/DeveloperTools/Conceptual/WhatsNewXcode/00-Introduction/Introduction.html
Highlights Found in Xcode 4.3
Xcode 4.3 supports development for iOS SDK 5.0.
The Xcode 4.3 installation includes Mac OS X SDKs for 10.6 Snow Leopard and 10.7 Lion.
The Xcode toolset is repackaged as a single application for a better Mac App Store experience.
Complementary tools, such as Instruments and FileMerge, launch from within Xcode.
The ARC Migrator can convert Mac apps that use garbage collection or retain release.
Xcode 4.3 offers additional bug fixes, stability and performance improvements.
These highlights are described in “New Features in Xcode 4.3”
Highlights Found in Xcode 4.3
Xcode 4.3 supports development for iOS SDK 5.0.
The Xcode 4.3 installation includes Mac OS X SDKs for 10.6 Snow Leopard and 10.7 Lion.
The Xcode toolset is repackaged as a single application for a better Mac App Store experience.
Complementary tools, such as Instruments and FileMerge, launch from within Xcode.
The ARC Migrator can convert Mac apps that use garbage collection or retain release.
Xcode 4.3 offers additional bug fixes, stability and performance improvements.
These highlights are described in “New Features in Xcode 4.3”