Extremely useful heater (after down clock and apply quiet fans), it runs 24/7 so you don't need extremely large power consumption to heat a house, and the electricity cost is compensated by the mined coins
i've heard bad things about health problem with an asic running in your home, there was one guy that had this problem
air get toxic after a while if too much heat is generated because of the fumes of some HW parts inside the asic