Forza 3 appears to be constructed 100% out of it. The screens in the Kotaku article are pure car goodness.
The series has long made me miss having a 360 -- the only games that really have made me want to join the Microsoft platform. The third game will be a Xbox exclusive, and the look of it makes my eye wander to the green machine. I hope I can hold out for Gran Turismo 5!
... giggity.