Yeah that would be awesome to have, however not sure how practical. IMO it doesn't outweight air cooled box by a lot. The only good thing about it is that it's completely quiet, however you can build/buy a specially designed box with passive air cooling, which also makes no sound.
Only thing WHY to have it is that it looks cool
Actually liquid transports heat in a much much more effective fashion than air.
A very practical example is when you are wet and you find yourself outside you feel cold real quick.
The reason this happens is that liquids(water in this case) remove heat much quicker than air would.
I dare to bet that this would take at least 5 degrees from your hardware.
Since I run most of my machines on OC this is a very attractive idea.
Another advantage is the lack of dust present.