Ribbon cable should be OK for the stepper motors. The important things are to make sure that each phase of the motor uses two adjacent conductors in the cable, and the conductors are thick enough to carry the motor current. The usual grey ribbon cable with 1.27mm spacing between conductors is probably too thin to carry the motor current, but the thicker (usually multicoloured) cable with 2.54mm conductor spacing should be OK. Don't put endstop and motor wires in the same ribbon cable.
The RepRapPro Ormerod 1 used 26-conductor 1.27mm grey ribbon cable for the heated bed. Two conductors were used for the thermistor, and 12 each to carry the current to/from each terminal of the 10A bed heater. It worked well, and it was only changed in the Ormerod 2 because RepRapPro needed to use shielded cable to meet CE emissions limits.
The RepRapPro Ormerod 1 used 26-conductor 1.27mm grey ribbon cable for the heated bed. Two conductors were used for the thermistor, and 12 each to carry the current to/from each terminal of the 10A bed heater. It worked well, and it was only changed in the Ormerod 2 because RepRapPro needed to use shielded cable to meet CE emissions limits.