Looks like it has some severe limitations when it comes to interactive object-oriented programming:
> Changes to a data type that affect the layout of an object, such as data members of a class.
The Common Lisp Object System does not have such a limitation. The price to pay is some indirection. You don't even need to create new instances from your class. The existing instances will be updated for runtime changes: different inheritance, new slot, removed slot, different class, ...
