i always turn it off, including modem... but i have heard people say it's like an airplane: once you are cruising there are few problems, it's the taking off and landing that can cause problems...
i leave mine on all the time, probably once a month, sometimes less, i will shut it down for one night. its a waste of time to shut it off, and it uses not as much power as some people would think..if your power bill is expensive its because of - washer/dryer, air conditioner, furnace, dishwasher...and a few of the other huge appliances. unless your on wellfare you have no reason to turn it off at night unless tis in ur room and u dont like the noise, but mines in my room and i dont mind the noise one bit.
With 11 total fans mine sounds like a jet, I could probably get used to it but I'll pass.. I probably will when I decide to goto watercooling.. biggrin: