Did anyone forgot this?: http://us.gran-turismo.com/us/news/d5147.html
It's GT5P with new physics. Nothing more.
The demo was specifically designed for this competition to showcase the realism of the brand-new physics engine and to challenge players driving skills using professional driving physics and many of the driving assists disabled. The full Gran Turismo 5 will feature multiple driving assists and various settings that can be changed to make the game easier or more challenging and realistic.
It's GT5P with new physics. Nothing more.