Heck yeah, riding when its really cold is naughty bad ***! On the rare ocassions in Tx when we do get a bit of snow (mostly ice) I've bundled up and rode (veeeeery cautiously and on the froz grass), it definitely makes me feel like "kiss my *SS, i'm out here digging it and you're not!" Learned that 'yes, virginia your deraillur will freeze up' and the slip 'n slide bike is really a *trip*!
I also will do a bit of running and the complete silence surrounding me & my dog when we have icy weather is really peaceful. Along with being the only 'crazy' outside in the cold too!