Yes, I got DUE to talk both ways w/ my old ATmega328p using series 1 radios and this library. No special changes needed. I don't use softserial, i connect using the hard serial lines.
I connected xbee pin 1 (i think), to 3.3V, pin 10, to gnd, pin 2 to rx, pin 3 to tx... The pin numbers may be wrong, but from the top left that's what they were. Dout I know goes to RX and Din goes to TX to get two way comms. No logic converters needed for DUE like w/ my arduino 5v stuff.