I'll make my comments short here before I knock out for the night.
First thing I noticed besides the graphics is that the game runs a lot smoother than before. It just looked like a nice, large leap from Forza 3 to me. The handling, like any new game, took some time to get used to & as I play more & more, I'll start to run with a couple of the driver aids off once I'm more comfortable with the controls.
Regardless of this steering assist debate, the cars all handle quite a bit more realistically than in FM3, imo. I found it without a doubt, quite easy to kick the 458 & M5 tails out in the turns if I was just trying to gun it through the corners. Even with TCS on, it was possible to start breaking traction in the rear if you were coming into the turns a bit too fast. All in all, a plus for me. I don't know if it was the new physics as well, but I quite enjoyed driving more in the cockpit view than in FM3. Everything seemed to be a lot smoother.
Sound wise, it's terrific. It's not cranked to 11 like Need For Speed, but it is more audible than in FM3. FM3 was good, very good, but you can hear where T10 made the improvements to give the cars a much more authentic sound. The backfire is a nice plus as it's random & not always the same noise. There's no "burble" (as far as I heard) effect like in Hot Pursuit, but it's a very minor oversight.
To end it, if the game plays anything like the demo, I will be very happy. I like the Rivals mode & I really like the traffic you have to race through in 1 challenge; almost feels like a "highway" mode.
But, again, I think it's very interesting & should make beating other folks' times very challenging when you have to decide if you can beat the AI into a turn, or keep the car in control as you take the outside. I'll also add real quick that the sense of speed looks to be very much improved. I think above 160-170 down the straight, the motion blur kicks in & the sound changes up a bit.
All in all, Oct. 11th can't come soon enough.