I have a pair on Nokian "Extreme 294" tires, which I put on my 26" mountain bike. Studded tires make winter trail riding a much more predictable activity. If you can find a frozen lake with no snow on it, riding is a blast!
I found a pedestrian in the middle of a local lake who snapped this picture for me. I was clipping along at speeds up to 20 MPH with traction that felt like dry asphalt!