Dewfpo,
I have used my Michelin Latitude X-Ice tires on my D Series twice now. I did not have any noticeable slip yet. I was blowing with my 240 blower uphill on a 12% grade. I could never do that last year with my tracked skiddy. I have a set of pewag chains in the bed to put on in case it gets tough, but not even close so far. I bought the chains from Century tire in Denver for the Michelins for $80 a pair. Century is great for tires, chains and such for yellow iron (and white/orange iron) and trucks.
Century Tire Inc., The Contractor's Tire Source. So far, I'm really pleased with the traction on these specialty tires. They are rated for "no chains necessary" on most passes in the west.