In short, yes.
I just finished a 15 minute race on Apricot Hill, with Kaz' 24H GT-R. I had slapped on a turbo and detuned it to meet the 650 PP restriction (the turbo ups the HP to over 900 HP in several 24H cars!). I had to really work to keep the ideal line, and the car felt a lot less like it is on rails.
I won that race with .2 seconds, as the AI really clings on you as you race. I haven't tried RS tires yet though, only RH, but I do think that RS would be more like the soft compound qualifying tires used in real life racing, after I have raced with the hards.