Objects and messages good, classes and inheritance mostly bad.
Except maybe for modelling/simulating concrete classes of objects (ie, as in Simula, the language).
Proper multiple dispatch (a la common lisp CLOS) seems rare - I'm guessing java/c++ seemed like a sane trade-off for some type safety - but they probably should've stuck to self/smalltalk (for Java) or looked to standard ml/common lisp (c++).
I still don't understand why Javascript got classes, rather than some paint on the prototype system.
