MSI's high-end P7N platinum board can cope with four SLI cards, but Nvidia currently wants you to use three cards only.
The new motherboard has two blue PCIe 2.0 16X ports, one white first generation PCIe 16X and one yellow which is a first generation 8X speed. All together, you can plug four graphic cards and have them working together but you cannot plug four dual slot cards.
If there was a driver, you would be able to plug four 8800 GT and get eight displays or some performance increase but so far Nvidia markets Tri SLI as a 8800 GTX / Ultra feature only.
MSI also uses dual channel, four phase PWM and it is supposed to be a very good overclocker. Even the Nvidia's additional PCIe lane chip has a heatpipe cooler.