Stealth.Pilot, I am with you. I had a chance to look at a friend's MCB M5 with the front and side black grills and I did not like it. I am sticking to the chrome grills. Unlike others who seem to love the black grills no matter what body color, I did not find it pleasing at all in person on a monte carlo blue body, and I finally decided not to go for it anymore when my gf made the comment that it reminds her of car owners who would change anything chrome such as badges, decals, etc. on their cars to golden (in the NYC area the owner would be unjustifiably identified though may not be true, as being a "pimp" or "dealer").
Also as what stealth.pilot has said, the grills should act as accents to the car. The black grills may look nice on a white or light colored car body but not on a dark one such as monte carlo blue. Looking at a picture of an MCB M5 with black grills, one's eye seem to wander aimlessly from one area of the car to the other randomly, whereas on a the car with chrome grills, one's eye is immediately focused on the grill then to the side grill. In photography/film, this is what you need to do to get the viewer to focus on a specific area -- increase/put contrast between the light and dark areas. Viewers' eyes will focus primarily on the brighter area (light colored grill in a dark car body). In the case of a light-colored body and dark grills, viewers primary focus will be on the body. When there is little contrast as in the case of a dark body and dark grills, there is no area where the viewer's focus is drawn and viewer's eyes just wanders.