Apple has just released Xcode version 4.5.1 in the Mac App Store, which includes bug fixes, as well as extra stability when targeting the iOS simulator.
It’s definitely a recommended upgrade for all iOS/OS X developers, so if I were you, I’d go right ahead and upgrade. The last major update to Xcode, version 4.5, brought along the SDK for Mountain Lion and iOS 6 and well as Retina enhancements and more.
