I've spent the last week in a training class for iOS (Pragmatic Studio's class), and have been developing with XCode and AppCode side-by-side (not just the obvious GUI stuff, but the actual code editor in XCode).
I was totally blown awy with how much better AppCode was compared to XCode. It identified all sorts of memory leaks that XCode needed a seperate static analysis tool to find, and was way faster to create code in. Even though AppCode doesn't have as much functionality with refactoring as IDEA currently does (creating a subclass, for example), the code completion and general ease of use made it a clear winner.
Just by using a faster tool, I was ususally the first (or one of the first) in class to finish excercises, and I'm just not that much smarter than the other guys :)
Keep up the good work, guys - I'm looking forward to the nexe EAP release (after I upgrade to Lion, of course).