More cons than pros:
Don't like the time it takes to layer all of my clothes.
Mechanical mishaps are more dangerous in cold weather.
Rain in anything less than 40ish really sucks.
You really have to watch the weather to be aware of any icy spots on the road.
Pros:
it's a change of season, getting away from the sweltering heat of summer.
forces me to take some days off of riding at all, since I don't bike commute when it's snowing heavily, or ice on the roads (mileage for the year so far is 5,200... need to build in some recovery days, at least for me)
For me, I'd like fall/spring weather nearly all year, with a touch of summer for a month or two. An even shorter 'touch' of winter, maybe for a couple weeks, tops. Then I'll be ready for warmer weather again.