sanyo denki 103g771
hi,
stepper motor is driven by supplying voltage to its coil in a particular sequence. ULN is simply a current regulator and it can supply the current required by the stepper motor (550mA). We use ULN only to provide the necessary current as this cant be supplied by the microcontroller(PIC, ATMEL, ATMEGA, etc.).
So as long as ur coding is correct ur motor will run. However you may have problems with the back emf of motor,,,for that you can use diodes for fast decay of current(this is the testing phase).