Nah, I don't mind people bumping old threads, if it's on topic and they have similar goals as the orignial poster.
Yes, there is ripple on the voltage, when no capacitor is connected, but it's not as bad as a single phase bridge rectifier. The simplist DC motor has three poles on the armature, giving the same waveform as a three phase full bridge rectifier. Most larger motors have more poles on the armature, giving an even smoother waveform. A lot of the noise is from arcing in the commutator.
A motor with a capacitor connected to it will mechanically behave like a flywheel. It will be difficult to start the shaft turning, as the discharged capacitor will act like a short circuit. As the capacitor charges, the shaft will become easier to turn, as the voltage on the capacitor approaches the average the back-EMF generated by the motor. If the shaft it left to freewheel, it will spin for longer, than it otherwise would, without the capacitor connected, as the capacitor will dischage back into the motor and power it.