It's rare that I'll embark in the rain. That's just.... nuts. But I've embarked many times knowing I might well get rained on. Fenders are key for me; I can't stand getting wet from my tires. Also, a windproof jacket. That's more important than waterproof for me.

My rain bike next winter will have fenders and 28's. There's a lot of tree debris and gravel (if it's snowed yet that winter) on the road and I think the step up from 25's, which I used this winter, be be safer and more stable in that stuff.