I'm using version 2.0 with iOS7 with Xcode 5.x with ARC enabled.
When I copied your getting started code into my project, the Hello World headers don't expand to show the content. When I checked, the pointers returned by contentForSection: are null.
If I run your sample code, it works correctly. I can't see any differences in the project settings, but there must be something.
Any thoughts or suggestions?