To quote from the article:
But most importantly, Smalltalk is fun. It’s fun because its programming tools make use of Smalltalk’s superior reflective capabilities to provide a development environment unlike any other.
Smalltalk is also fun because defining and using domain specific languages isn’t an afterthought, it’s the only way Smalltalk works at all. As a result, Smalltalk code lets both the reader and the writer focus on the problem domain, using language and notation that is natural to that domain.