VEHICLE RELATED:
Wheelblur:
1. The wheels have blur and the tires don't.
2. The blur makes the rims look fake and flat, sofar I think only the Camaro and 300SL had wheelblur which didn't make the rims flat-ish.
Wipers: where are they? We haven't seen them yet, and I personally think Eden will not implement them to avoid having to make flexible wipers that follow the curves of a car windscreen. I hope though they'll be in. Rain = wipers.
Rimcolor: rims like the ones on the TT-RS and DBS look a bit fake-ish, perhaps because somebody set the reflectionamount too high. I'd suggest a closer look at rimfinish properties, most rims, even on exotics, really hardly reflect anything. It'll be better for the diffuse color of the rim to show up a bit more real.
Car-world-allignment: I noticed it most at the Shelby pictures: the wheels stick through the ground.
ENVIRONMENT RELATED:
Reflections: roads reflect everything except cars. The cars only show up with a solid dark shadowplane below them.
Offroad: I'm still a bit concerned about people being able to complete offroad challenges with high-end supercars, the routes still look too smooth and flat.
Trees: as many pointed out, the airport needs to be cleared a bit of trees, because we all saw planes flying through the tops.