Hey MadDog,
Yeah, I'm just starting to look into this and my initial impression is that it is the surrounding package and not the chip surface itself that may be causing people problems. The plastic package moulded around the nF2 NB is definately higher, and prevents the heatsink from fully contacting the chip. The wad of OEM bubble-gum more than takes up this space...
Still, my real question is whether or not the chips themselves (GPUs and NB) are flat like a CPU or if there is some difference in the manufacturing process that makes them curved???