Other than the obvious problems of oil submersion, it stays cooler now that we have it all squared away. Plus it looks awesome. I can't imagine getting stoned and watching that tank, it's mesmerizing enough sober!
I've heard of people doing that. it has some major pros and cons, the biggest ones being the components are now covered in slimy goop, and in submersion you are cooling a lot of things that don't need it.