This dicussion
thread points out what I have been saying about how generics changes the
Java langauge. Generics also change how we think about the programming solutions that we implement. Some techniques, such as a list of unknown objects, are still possible, but the addition of generics points us away from thinking in these terms. Generics encourage us to think in terms of a specific type, or set of types related by a common superclass (other than Object, of course).
I think that it will take the Java community a year or more to fully come to terms with the implications of generics.
Java is changing, and we will have to change with it.