I'm fairly certain the noobs will be asking about this product between now and Whitney Prime Time.
I've owned PreCip stuff for the better part of a decade. My feeling is the stuff is waterproof, marginally breathable and highly ventable.
Case in point was a recent outing where it rain and snowed the previous night, I started the trip with my PreCip jacket on because I expected a lot of fall out from the tree, both rain and snow depending on elevation. I had the jacket fully vented at all times. When I stopped for lunch, the interior of the jacket was soaked with perspiration and the back of my pack was soaked from the same. The stuff did what it was supposed to do.
My biggest use my jacket and pants are for wind protection. Three of the times I have summit Mt. Whitney I had either PreCip or Gore-Tex pants on for wind...not rain. And, I should have had the pants on for a fourth.
