We've already got electric motors that are over 90% efficient, so there isn't much room for improvement there even if these are more efficient. The trouble with electric cars is with the batteries.
The maglev trains and electromagnetic roller coasters need electric power to drive them, just like their wheel or chain driven counterparts. It wouldn't surprise me if some of the electromagnetic coasters store their energy in some sort of ultracapcitor. Now those are a technology that might get some useful results, as they can store a lot more energy than a same sized battery.
