Ive owned this car for 1 year and have owned 2 other W220's and honestly don't remember any "click"....funny how you get used to something and it so routine that it could be missing and I would not know it. When I put the smartkey in, it turns easily all of the "accessory" functions (radio, dash lights, a/c blower etc) come on it's just doesnt kick into the start function. As I said before if it matters it is not unlocking the steering wheel or transmission.
Before I call a wrecker and have the thing drug up onto a flat bed in the morning some one please tell me if its the starter motor, the smartkey or a operator failure...lol