Not done much testing yet but so far i have found the following:
1. Control Profile has been reset.
2. Sounds for road noise, tyre scrub and another sound(can't remember what now) are set to 0%
3. Introduction of a graphics monitor, where you can set a desired FPS rate and the game will adjust the graphics automatically to keep the game running at the desired FPS.
4. The HUD now has 5 or so settings, before you could either have All HUD, Just the Rev counter or nothing, now there are more options.
As for the new cars, i can't say much yet, but early indications are very good.
I agree with Scyp the 260BHP is my favourite at the moment, i tired the 320BHP around Brands and it was bouncing all over the place, due to bumpy track and immense power, however around Monza it was pretty awesome to drive.
These cars will provide for some real fun and intense action in on-line races.
The whole game has been spruced up and is now quite a comprehensive game as you can now choose between the WTCC cars (9 models), 87 cars(2 models), Minis(1 model) and Caterhams(3 models) and 12 tracks.