I just install and run this kit with no problem.
I learned about it from this thread
Using cakekphp 1.3, apach, linux
1. Download http://www.ohloh.net/p/cakephp-debugkit/download?filename=debug_kit_1.2.tar.bz2
2. extract it under app/plugins/debug_kit (doesn't work without the underscore)
3. Add debug_kit tool bar to app_controller.
In my case var $components = array ('Session','Cookie','DebugKit.Toolbar');
4. Didn't change my debug level, Configure::write('debug', 2);
I get a long list of debug properties in the bottom of the page which I presume is what I should get from this kit.