Thought-out and convenient code navigation and code completion
On the fly code analysis with quick-fix suggestions
Project-wide usages search for classes, methods, variables, resources
Instant code transformation intention actions, including i18n support
Better code refactorings: Change Signature, Extract Method, etc.
Can open and create Xcode projects
Integrates with the Interface Builder
Can run your app on iOS device or in simulator
Unit test runner for OCUnit
Has a debugger with evaluate expression
Supports Subversion, Git, Perforce and CVS version control systems

Link for more information: http://www.jetbrains.com/objc/