In reality there is no real evidence,however i do not think there has been a car that has been so intensly tested as a new model (1 million miles plus) also every part of the car has been checked and rechecked ,not only for weight but also for quality,as with many cars i dont think price is the main concern.
i think Mclaren is known for reliability because of their attitude towards potential problems,nothing is perfect but they are putting in place a selected dealership network that have been picked more for customer service than for sales.
All dealers must carry at least 1 of everything on the car(except the chassis) so any problem can be delt with asap,their mantra is for every customer to be back in the car in the shortest time possible if a problem occurs.
Im sure everyone on this site has had that problem with a part holding up work on your car,i have had porsches for over 25 years,one such problem kept my car in bits for 6 weeks,just a simple gasket,but i still see them as been reliable! Only time will tell