Just wanted to let people know that I am very happy with my NEOS overshoes. For the first time in my life my toes are not cold!! The overshoes are very wide, with lots of space to fit whatever you like underneath.
I don't, in fact, wear them with shoes, but with my down-filled hut booties! Coupled with a liner sock and a Smartwool outer sock, I can wait for the bus at -20 with no problem.
I have also worn this combination for snowshoeing excursions, and it is true (as Damien has pointed out before) that they are not that breathable. The down booties were soaked with condensation by the end of my hike (but my feet were still warm). And since I then just hoppped into the car to go home, it didn't really matter. If I were going to be out all day, or for multiple days, with periods of lower activity when my feet would have a chance to cool off, this moisture would obviously be a major issue. If I ever reach that level of outdoor winter activity I think I would spring for some of the mukluks others have mentioned ( for example: http://www.toesalad.com/node/1256 )
However, for my purposes - day-to-day bus riding and city walking, playing in the snow with my daughter, and occasional active use - this combination has been highly satisfactory.
My only refinement next year will be to try some Yak Trax on really icy days. I have been wearing Stablicers this year. They do a great job on the ice, but are only hanging on to the boot by a thread - the boots are a little too wide (Stablicers are shaped like a traditional shoe - too narrow at the toe and barely stretch around the boots). The Yak Trax look more adjustable.