If you're worried about pipes freezing (at 50*F) leave a faucet or two trickling. Moving water takes much colder temperatures to freeze than still water. At 50*, I wouldn't worry about the pipes unless you have a real drafty house.

Something to think about-

Air heats up much more quickly than more dense objects/materials. When you come back home, it will take the 'house' much longer to get to temp than the air. So your furnace may shut off at say 70* the house will feel colder than that until everything is able to absorb the heat and come up to that temp.