I’ve just ported the new features of php 5.3 in my own framework.
Especally the autoloading is very simple when you are using the namespace feature. If you create the directory structure analog to the namespace you don’t have to search the class file in your directories. I don’t like long class names which represent the directory path to the class file. With namespaces you have short class names like i loved in java.

I missed in your example the following notation without alias:

use your\namespace\ExampleClass;
$obj = new ExampleClass();