Studded tires are indispensable if you have mainly plowed roads but might sometimes have ice or snow packed into near-ice surfaces. That's what I face most of the time.
If you're really going to be commuting in deep snow and will not be hitting ice, you want wide knobbies for flotation. If it's going to be a mix of deep snow and ice, then you want the wide knobbies with studs, and be sure to get tires with studs part way up the side of the tread; those are good for climbing out of ruts instead of allowing the rut to throw your bike out from under you.
See
http://www.peterwhitecycles.com/studdedtires.asp - read the page. It's got a ton of good info for lots of different conditions.
Honestly, I have never seen any report on KTrax, but I can't imagine that it's useful. It wouldn't seem to preserve any momentum, and if that's the case you'd probably get there faster and easier on cross-country skis. I've skiied to work a few times.