It's fun, you can't put the hard drives in the liquid, and unless you mitigate the oil that weeps up wires etc, it's a mess. You also need to cool the mineral oil with a modified radiator setup with fans and a pump if you run it 24/7.
One store (still on the web was able to run the office PC all day, but if left on overnight, the liquid was too warm and the PC wouldn't boot, and it took a DAY to cool down. They didn't have a radiator to remove the heat.
Fun, but wayyy not practical.