I would ask Nikon for their compensation for the long time they have let you without camera (Aren't they suppose to give you a loaner camera if the repair is beyond certain amount of time? Honestly I would think not but worth’s to bring it out). Then mention them you other friends who bought Canon without faulty Sony's sensors are much happier and are this what Nikon answers to its faithful consumers? Make sure to mention them you will reflect the outcome of this on the net and in particular, in world wide visited specific photography sites.
I would ask them if the camera is having so many problems that has taken so much time, why aren't the replacing it with an equivalent new camera or give you adequate, reasonable incentive to buy a new one.
No matter what you say make sure you are polite all the time. You may raise your voice but only in a polite fashion as the customer service person generally have that ability to bring you to the level that you get out off your mood and that is the time that you have lost the battle.
Don't give up when you know you are right and be patient little longer.
