1. Youd need a pretty decent sized tranny cooler or radiator to cool the oil.
2. Youd also need a pump capable of pumping the very thick oil.
3. Youd have to find a place outside the case to mount the power supply
4. Upgrades would become nearly impossible.
This is from Puget
"The system under load was a different story. We started 3DMark06 looping, and watched the temperatures climb. It took a really long time. After an amazing 12 hours, the system topped out with a CPU temperature of 88C. Yes, that is really hot...on the other hand, the system was rock solid and didn't crash when running 3DMark06 for 48 hours at these temperatures. While you could add some radiators and pump the oil through to cool it, you realistically would not be gaming constantly for 12 hours, so these temperatures are as extreme as it gets for this system."
As for the cooling system(which isnt needed but can be installed{read the article on the Puget gaming website}) just use.
http://www.zalman.com/eng/product/Product_Read.asp?idx=183
The power supply can be put in the mineral oil.
Upgrades are not impossible just very messy
And the poor overworked fans. You think you
would want to take them out so they're not
working through the liquid.
They stated in their article that they havnt noticed any change in speed on the fans after two months of continual running. Plus if the fans break... Oh well
The system wouldnt need them to run under water.
Just throwing that in.
Also, this is EXTREMELY cool, i have never seen a liquid submerged computer before. It almost makes me want to get the stuff and do one my self. I say go for it man!