Just received the P4P800 today; swapped out the MSI 645DX. The surprises!! Well, not at all, something that I might have expected all along.

MSI board idle 42C Load 60 C (room 26C)
P4P800 Idle 32C Load 47C (room 26C) These temps are within 1-2C from the external temp probe.

MSI board 12 volt rail - never seen 12 volt since I had the board for two years; topped 11.7 Volt Lowest 11.3 Volt

P4P800 - tops 12.10 Volt lowest 11.73 Volt. Using the same power supply; same Ocing the 2A to 3.0 Ghz.

Conclusion:
1) Temp reporting from boards are highly inaccurate for P4s'.
2) Power Supply must work with board; can't single out the power supply when the board is way undervolted; or vice versa.

Summary:

Quality control sucks .....
Asus Intel Board always report lower temps.
Abit reports higher; same as MSI.