i made the mistake of using the winter yeti with the reflective liner... when it wasn't winter.
its a very lightweight, packable piece of gear. the one i used was very very puffy and extremely warm. the only relief i got from using it was the fact that it kept falling off my left shoulder and it vented it.
Did you have the QU oriented correctly with the head end at your head? I had this problem before I figured out there was a head and a foot end but since I started hanging it properly I haven't had the problem again.