Recommended way to declare delegate properties with ARC

Question

Xcode 4 Refactor > Convert to Objective-C ARC transforms:

@interface XYZ : NSObject
{
    id delegate;
}
@property (assign) id delegate;
...
@synthesize delegate;

into:

@interface XYZ : NSObject
{
    id __unsafe_unretained delegate;
}
@property (unsafe_unretained) id delegate;
...
@synthesize delegate;

If I remember correctly it is also mentioned in WWDC 2011 video about ARC.