Danielo mentioned that he switched over to his Kenda Klondike studded bike tires a few days back, and feels very comfortable on 'em.
In the bike rack at the office, there are four bicycles today - two of the four have studded tires. One is a "mountain" bike with some nice-looking Nokian tires at both ends. The other is a touring bicycle - very similar to my own - with fenders and some nice Schwalbe tires. A guy said he actually saw some studded bike tires at Wal-Mart. Weird. (I'm confident they would've been in 26" mountain-bike size.)
When the snow falls and the roads get covered with slippery stuff, it always puts me to thinkin' about studded tires. But the pleasant reality is - here in Boise, Idaho - it's rare (but not unheard of) for snow to stick for longer than a few days, or a week at the most. So, do I buy a $100+ set of tires that I'll only have legitimate use for, maybe 10 or 15 days of the year? So far, I've resisted for strictly financial reasons.
(I haven't missed a day of bicycling so far this time around. One icy afternoon I had a distant caroling gig, so I left the bike at the office overnight, and caught a ride with a colleague. The next morning I took the bus to work, then rode home in the afternoon.)
Peter White, of the New Hampshire bike shop named after him, has some good information about studded snow tires HERE, if you want to study up. There is a wealth of information on his website about everything-bicycle. (I also lifted the cool photo - of his shop - from the website.)