OS X interface designer has an interesting feature for Objective-C that I would love to see in a Java IDE. It allows components to be bount to another object via drag and drop. Objective-C has loose typing, so you don't have to implement every unused method in a listener's interface; but I imagine IntelliJ could find a way around this.
Visual Age had a similar feature that let a component be bound to a value object. The generated code was nasty, but IDEA doesn't have to show that garbage anymore.
If this can't be added by IntelliJ, will the API be opened up for extention?