Many short-distance (< 30 km) ferries in the UK that sail in busy waters (i.e. harbours, ports) have them, and generally they're very reliable and low-maintenance.
One of the disadvantages are the draft required, and it is a concern for grounding, so many have plates underneath for protection.
I hadn't heard before about ferries using Voith Schneider propellers. I did know that many ferries use (somewhat more traditional) azimuth thrusters for good maneuverability.
One of the disadvantages are the draft required, and it is a concern for grounding, so many have plates underneath for protection.