I have to admit, I didn't read through the great tuck & roll debate, so apologies if any of this has been posted already.

My main gripes with clipless in winter are, 1st the cleat is a great heat sink in really cold weather. I cannot use my normal summer SPD shoes anyhow, because there's not enough room for added socks/insoles. I have proper winter boots for that, and I'm not going to put cleats on those. Besides, a mechanical problem that you'd be able to fix in 5 minutes in summer may force you to walk the bike in winter. Better have shoes that actually make that possible.

2nd, I've fallen once while clipped in (the good ole "forgot to unclip at red light" incident). The worst part of it was, it's extremely difficult to get up again when you're lying on the ground still clipped in. And this was in summer, I'd think it's even worse in winter. I'd rather have my bike under the bus than the bike plus my still-clipped-in self.

In my experience studded tyres help a lot on black ice. I have been able to recover small front brake lockups on ice with studded tyres. Lots of luck is usually involved (front tyre pointing straight forward and/or no pressing need to stop right there), I just let go of the front brake, but I know I would crash more if it weren't for the studs. That, or ride a lot slower.

--J