I have high tech breathable rainpants and jacket. No poncho (I hate ponchos - not breathable at all and tend to snag on things)

Have I ever actually USED the rainpants? No. I guess I've been lucky in that the rain I've run into has been wet rain, not cold rain. Even the sleet storm at 11,000ft last summer didn't prompt me to put on pants. Bare legs sticking out of my hiking shorts have been just fine so far. But I always carry those wind/rain pants and jacket for any long-ish or high altitude hikes. The choice to gear-up or not depends greatly on the circumstances, how far from the car you are, the likely duration of the bad weather, your altitude, etc.