yeah that's what I said -
"it's like a combination jacket and poncho in that it has arms and shoulders like a jacket but no front entry. instead it is a pullover and the front half is separate from the back, like a poncho, which allows for ventilation."
and - "...it's designed to go under, not over, your pack." that means you would still need a pack cover.
if you look at these 4 items - jacket, poncho, pack cover, and Packa, the Packa is the only one that covers all the bases, and that's a pretty neat trick when you get right down to it...