Just completed this (main tour, 75% in stats), thoughts below:
+Feels like a decent amount of races, says ~9h45 behind the wheel which I guess translates to about 12 hours total, although I'm sure it took me longer than that (no doubt due to Codemasters obsession with intermission screens!)
+Graphically very impressive, one of the best looking games I've played, even the people near the road, trees etc look decent
+Excellent performance I ran with most things maxed generally 90-120fps
+Racing feels generally OK although maybe a little bit arcadey
+Good roadside physics in terms of destructable roadside objects/fences etc
-As mentioned above, it's annoying having to click through a dozen screens between every race
-Saved vehicle setup profiles take as long to select and apply as it does to manually change it :/
-Stupid fake purple video card artifacts when you crash, at least it's not as bad as in Batman since it doesn't look like your PC has locked up but still annoying as I was overclocking
-Felt like there wasn't enough variety of environments/tracks, I don't really feel any great desire to go back and get 1st place in the remaining events now I've beaten the main game.
-Some of the Gymkana events (typically complete xx challenges within a time limit) are very frustrating, towards the end I just skipped those events altogether
-Superseries final is way too easy, set in Monaco which is a very smooth track meaning you can get away with very low rideright and stiff suspension, I just blew them away in my Audi Quattro
-Felt like drift events were a bit underutilised, I only remember about 3 of them?
-Voiceovers felts more contrived than usual
-Graphics aside, not as good as Dirt2