Xcode 4.1 Developer Preview 4 | 4.34 GB
This is a pre-release version of Xcode 4.1 for both Mac and iOS development. This release requires Mac OS X Lion Developer Preview 2 Update 2 and includes iOS SDK 4.3. Continue to use Xcode 3.2.5 or Xcode 4 on a Snow Leopard partition if you plan to submit Mac or iOS apps to the App Store.

Apple has released Xcode 4.1 Developer Preview 4 to Mac OS X developers.
This release adds IB support for NSPopover and NSWindow animations and behaviors among other enhancements.