Our next generation silver compound will perform better than any of our current compounds. There are too many variables regarding contact areas, pressures, surface finishes, surface run-outs, and power dissipation to put a number on the difference.
The AMD warranty issue has received a lot of coverage, much of it incomplete or misleading.
The fact is that using ANY thermal grease or ANY heatsink other than the stock heatsink with the pre-applied thermal pad that came in the box with a boxed CPU will technically void the warranty on an AMD boxed CPU.
Shin Etsu G749 can be used by system builders to temporarily mount a heatsink to a new CPU to verify that the CPU works. Then the G749 must be removed and the stock heatsink with pre-applied thermal pad must be mounted on the CPU before the computer build is used or sold.
So on the boxed processors, you MUST use the supplied heatsink and thermal pad to maintain the warranty.
As the AMD warranty says:
This Limited Warranty shall be null and void if the AMD microprocessor which is the subject of this Limited Warranty is used with any heatsink/fan other than the one provided herewith. http://www.amd.com/us-en/Processors/TechnicalResources/0,,30_182_867_2139,00.html
One thing that is often misunderstood is that AMD only provides a warranty on their boxed processors.
As they say on their site:
AMD's Limited Processor Warranty does not cover non-boxed products purchased from resellers.
AMD only provides a warranty on its line of boxed processors.
There is no AMD warranty on OEM "tray" processors so there is no AMD warranty to void by using thermal grease or a better heatsink.
I hope this helps clear things up,