Following my flying training my instructor demonstrated a circuit using only rudder and trim and power settings (in a Cessna 150) to simulate aileron and elevator failure. I wouldn't like to try it myself, but it certainly showed me that such failures would be survivable so long as you identify them early enough and keep a cool head. I guess much depends on the plane though - I'm not sure I'd want to be spinning the overhead trim in order to flare a Cherokee, for instance.