I used a coated nylon poncho for a few years in rain and snow. I was pleased with the performance overall. It was dry, but had the common compliant of hot and sweaty. So I figured I could lose a few ounces going with sillyon of the same size. After a couple of treks in the rain I found that the sillyon soaked quickly and was just as hot and sweaty . I would have been better off without it.

So the sillyon has been stuffed and mounted and now I carry a little more weight but functionally drier poncho/cook shelter. Depending on weather I have a rain suit and use a pack cover as an alternate.