See What’s New in the Xcode 4 Developer Preview
iPhone and Mac Developer Program members can now download a preview of Xcode 4, the next generation of Apple’s integrated development environment for creating iOS and Mac OS X applications. With a brand-new interface, compiler, debugger and dozens of new features, Xcode 4 is faster, easier to use, and more helpful than ever before. Quite simply, Xcode 4 will help you writer better code. Read about the many new enhancements in Xcode 4 and download the developer preview today.