I run a Barney's Supercub jacket (which is a Integral Designs Rundle, but with a tougher outershell), and Mountain Hardwear Compressor pants. Not the most UL puffy system, but its part of my overnight emergency bivy away from camp on the mountain system, so its worth the extra weight, especially the two nights last year when I didn't make it back ot my camp and sleeping bag. I prefer synthetics over down for puffy clothing due to the fact that the chances of it getting wet are a bit better than my bag. So I'll take the weight savings of the down sleeping bag and apply it to the puffy jacket and pants.
I layer over my Supercub all the time. Either my eVent Integral Designs Thru Hiker or my Chugach Rain jacket from Kuiu work well in layering. The stouter shell just means I have a bit longer before I HAVE to dig for the rain gear.