1. There are some methods common to all objects, like toString:
How could you have written such code without Object?
2. The Collection Framework (java.util.List, Set, Map, etc...) rely heavily on Object to allow the defintion of general collections:
The current version of Java (1.5) compilcates this point with generics, but the argument can still be made: Having a common base class is very useful. C++, as you may know, lacks this, and most C++ Frameworks begin by defining base classes that most their classes derive from, directly or indirectly...