Dealer's choice...but I see no value in leaving a computer on when I am away for protracted periods of time.
If I know that I will be gone overnight, I turn my two systems off. If I know that I will be absent for more than 3 days, I turn off the surge protectors that my computers, TV, etc. are plugged into.
As for the computer power supply itself...I leave its switch always on, once I install same or set up a new system. It has an internal circuit breaker which should protect the system (turns the system off) whenever I have a power failure/surge.
Edited by hamluis, 31 December 2008 - 03:04 PM.