the trails are not as enjoyable when it's all snow and ice. sure, it's doable, but you have to deflate the tires so low that it feels like you're pulling a car while you travel 'long the path...
i can't believe it! i got hurt! and... it wasn't even while riding! i was approaching a fairly technical sloped part that was iced over. i thought to myself "nah, i'll walk it - it's too dangerous to ride." get off my bike and my biker shoes, of course, slip on the frozen dirt... down i go.
it's just not as fun. the wheels would fall through the ice on the path, and the water would splash up, some of it onto the discs... and then my discs would be iced over. no braking power. i don't think riding in the sub-zero temps is too good for the bike anyways.
anyone ride during the winter regularly - during the winter in parts of the world where there actually is a winter?