We are using custom fonts in our project. It works well in Xcode 5. In Xcode 6, it works in plain text, attributed string in code. But those attributed strings set in storyboard all revert to Helvetica when running on simulator or device, although they look all right in storyboard.
I'm not sure if it's a bug of Xcode 6 or iOS 8 SDK, or the way to use custom fonts is changed in Xcode 6 / iOS 8?
The simplest answer that worked for is to drag the fonts into FontBook. If the fonts are in your project but not in your computer's FontBook, IB sometimes has trouble finding it. Weird, but has worked for me on several occasions.