Finally a decent motorsport sim to compete with the GT series!
I have not got much to say other than this, in my opinion the best driving simulation game ever made. With a huge selection of cars, ultra realistic physics/damage system which prevents you from playing pinball off the barriers and other cars and encourages you to actually race.
Some makes of cars, rarely seen in other games include Ferrarri, Astin Martin and Mercedes, top class. There are many competions to enter which become progressivel harder but never impossible provided you know how to tune your car well.