The lack of the ability to subclass has been galling. Take a look at the "Create your own collection" series, for example. Each of them emulate tables, but they need to do a lot of background hackery just to emulate tables. And it's hard to determine which subclass of tables it uses.
So I introduce "zen typing". You wear a blindfold (i.e. ignore the type) and just code as if the existing functions will work. Let the functions fight over how to exactly implement them ^^
