standby or off?

it all depends on what kind of milk u add to your cereal

seriously though, I leave mine on standby.  I'm not worried too much about it because it's plugged into a decent battery backup unit.  I'd say it all depends on how worried you are about surges and such. 

standby.

I leave mine on standby if I know I'm going to be turning it back on later that day or even the next day.

Any break in time longer than that and I shut it off completely from the back switch.