We've been over this discussion a few times over the years in the Winter Cycling section. I have a set of the Kenda made Nashbars and the studs are carbide. I also have run a set of Nokians on another bike and have found the wear of the studs on both sets of tires to be virtually identical. The Nashbar tires are three years old though, so there's always the chance that they have switched manufacturers.

My best advice for people who want to commute year round in northern areas is to have two bikes on hand, or at least a second set of wheels. Set one up in the colder months with studded tires. Without studs a patch of ice on the roadway will put your butt down fast. They are well worth the price.

There's a lot of good info posted in the Winter Cycling area on equipment and clothing, much of which would be pretty valuable to the year round commuter.