Love this bag, used it in the desert where it got down to about 25deg and was super warm, almost too warm for this human furnace.
The center zip is great but yes the zipper will fall into your mouth if you move around in your sleep. I also found that leaving it slightly unzipped alleviated this problem, but am looking into fashioning a Velcro tab to the bag and zipper pull tab to fix this.
Super soft bag inside, does leak feathers but only slightly, only time will tell if its a major issue. For the price i payed on SAC, it's more than worth it.
Stuff sack is great, can also fit more gear in with the bag as some have stated below. Storage sack is large and if you're unable to store the bag hanging or laying out in a dry place, is a great alternative.