Radical, McLaren, Callaway and Bentley (that sound) are really very good. Don't know about the Merc yet.
@marmagas seems to like the FFB in that car...I don't (yet) if I compare to the others. Don't know what's wrong, my wheel (Fanatec V2/Formula carbon) feels notchy (never had that feel in any car in any sim), while on the others it does not have this issue.
But, I updated to 1109 and now on some tracks (Ricardo Tormo to name one) the tarmac looks and reflects like water.
No flying dust when touching the grass/gravel either.
Edit: the 1109 open beta does not seem to have the issues I mentioned (at least not the water effect), but now I'm struggling with FPS. Had 23 FPS when leaving the pits and about 50 on track. Way lower than the previous open beta...