I think ponchos are most effective for UL hiking when used for both rain gear and shelter. You get the cost saving and the weight saving and your pack is covered too. They also provide excellent emergency shelter options for day hiking.
They aren't neat and clean looking, especially with the Gatewood Cape, and you just have to get over that. Ponchos don't work as well in high winds and I wouldn't even try bushwacking in one.
The Gatewood Cape is superior to a poncho, giving good rain protection and 360 degree coverage as a shelter for 11 ounces, while a conventional poncho really needs a bivy to give good all-weather protection. It also takes up very little space, so it works well with smaller packs. I'd LOVE to field test a Cuben version [wink, wink].
The snaps on the sides of a poncho help seal the edges. There's nothing wrong with using a simple belt from parachute cord keep it from flapping around and make the whole package a little neater. Those loose sides provide excellent ventilation, so you don't have to fiddle with pit zips and touchy laminated fabrics. A poncho would be an excellent first MYOG shelter project.
I do think of ponchos more for summer stuff, where you (hopefully) aren't spending all day in that rain. If I were going to the coast in Winter or shoulder seasons, I would probably lean towards rain jacket and pants and a storm-worthy shelter. Those hikes are short and flat too, so a couple extra pounds isn't a big deal.