I bike year round in Toronto, Ontario. Hybrids work great in the winter! My preference is to put skinnier tires with minimal tread on your bike and keep them very well inflated. This lets your tire punch through the snow and get traction on the road beneath. I biked home from work 11 miles through a half foot or so of fresh snow that hadn't been plowed from the roads a few times last year with this kind of setup . . .
Our roads are generally pretty clear of ice during the winter, so I've never needed studded tires.
Crucial for winter cycling:
- Lube! Lube the breaks, derailleurs, and chain on a regular basis. I also take about three water bottles of hot water to the bike after a wet ride to rinse all of the salt off. I've been using 'White lightening - Wet Ride' and it's worked well, but any decent bike lube will be OK.
- Full coverage fenders! Really cuts down the amount of crap that sprays up on you, and more importantly on your drivetrain.
- Lights! You will be biking in the dark if you bike in the winter. It gets dark MUCH MUCH earlier, and the lights also help when conditions are snowy.
- Brake pads! Winter riding seems to destroy brake pads pretty quickly, keep a spare pair handy.