This jacket is way more than a raincoat! On cold mornings when I know it will warm up, I start with this jacket instead of a vest and arm warmers. It packs away much more easily than those items when the temps rise, and if I have a lot of changing conditions (long climbs or descents, large changes in altitude, or variable weather) it is a lot easier to manage than vest and arm warmers.
In Tucson in the winter, this is the perfect thing to pack to the top of Mt. Lemmon! If it's 70 in Tucson it might be 45 up top, and this takes minimal room in my jersey but keeps me warm at the top and for the descent.