After a couple of offs on the ice last year I'll definitely be more circumspect in when/where I cycle this winter. Sub-zero temperatures overnight and I'll stick to a short flat route. Wet slippery leaves and I'll stick to Dartmoor on the MTB where there aren't any trees.
You can't beat being out in the countryside on a nice winter's day (I'm lucky enough to work outdoors in the countryside

), but for me the risk of injury and worrying about all the descents en route are significant factors in deciding whether to go out on a given day.
TBH I've been hibernating since March though, when I took my first ever job that required commuting by car every day... I have lost a lot of cycling fitness as a result, so that's definitely an argument for keeping going throughout winter when conditions allow.