these features got my attention first time I saw it,
  • The possibility to load class definitions and method definitions (which extend a class) at run time.
  • Objects are dynamically typed: Full type information (name and type information of methods and instance variables and type information of method arguments) is available at run time. A prime example of application of this feature is `-loadNibSectionwner:' method of NEXTSTEP's Application class.

I haven't gone further into the language because the syntax looked so alien from ANSI C which it it was suppose to derive from, the syntax is taken from Smalltalk which I have no idea of.