Agreed. Overall, the car’s shape is there, but the details that bring the car to life need refining.
As Hyst said, the rims are far too small for an M6, and the seams that should be tight and crisp are loose and bendy. Connections between body panels should be quite sharp and not deform the mesh more than a few mm away from the bend.
The top line of the windscreen isn’t a smooth curve in your image, and the windows need a chrome lining, and the pillar at the rear of the door is thicker and plastic-covered.
The beltline running up the side of the car is a bit too deep in your model, and the headlight shape does require some defining - the reflector case is not there?
The car is also missing the M-grille on the side behind the front wheel arch. (a common oversight)
http://www.exoticcarsite.com/pictures/Cars/bmw/645ci/bmw_645_ci-17.jpg
http://www.autoonline24.com/images/BMW/m6/2.jpg