yes jQuery.Deferred is a very elegant solution to nested callbacks et all....
I have got it at the heart of the Single Page Application Architecture I am building currently.
e.g.
stionaJS.DAL.authenticate(creds)
.pipe(listDomains)
.done(withMultiUserDomain)
.done(withSingleUserDomain)
.fail(failedAuthentication);
I hasten to add, combining this with KnockoutJS works wonders!
I really like the fact that jQuery's AJAX methods were converted to support this.