wrap/unwrap vs Go-style duck typing

[John Colvin]

On Friday, 25 October 2013 at 05:45:53 UTC, Andrei Alexandrescu 
wrote:
> Hello,
>
> I was curious how our fledgling wrap and unwrap routines 
> compare with Go's duck typing - similarities, distinctions, 
> performance. Please share any thoughts, thanks!
>
> Andrei

Are there some examples somewhere of when using wrap/unwrap is a 
good design choice? I can imagine it's convenient in some cases, 
but what's the "killer use".