I used to use the Endura neoprene overshoes commuting through the UK winters. They were very warm and good at keeping out the water, but they were way too fragile. They just about made it through a second winter but had little splits and tears all over them. I reckon they'd be excellent if you were just out for a long ride in the country, but if your commute involves traffic lights where you put your foot, down then sooner or later you'll kick the kerb or the pedal and tear the neoprene.
Although it's not quite what you asked for, my advice would be to splash out on some waterproof shoes. I hunted round for a bargain pair of Specialized Defrosters which are brilliant for winter MTBing and commuting - I probably wear them for half the year now.