from what I saw in the demo...NOT the Prologue itself...the AI doesn't stupidly ram you if you get in its way...it will avoid you, when 2 AI cars are battling, occasionally one will spin out...its no longer a processional race...the tires now make a difference...no longer are their tendencies simply to wear out quicker based on compounds (soft hard etc)...they'll actually slow you down...and it does make the 2 laps (demo), that much more challenging...in some cars you can't even get 1st place after 2 laps

(didn't say it was perfect)...
The prologue has online vs play...in an interview with the creator, he claims that there will be an update for damage...so the 3 things that bugged me with gt3/4 have seemingly been improved (+ WAY better graphics, and an inside view that's usable)..,
from where I stand this game is looking very very good...