Packs down really small making extra room in my backpack and works well right down to temp rating I suspect. The coldest it got when I was using it was 45, but I was sleeping naked in the bag and was completely comfortable. 3/4 zip is nice for warmer nights...I guess full zip would be preferable, but it does the trick. I wasn't sure why there was a big bag attached to the inside of the sleeping bag at first, but recently realized that it is for storing the bag in the long-term. The compression bag works great and it is cool to show off how small the bag packs down, but don't leave it in there all the time because it is bad for the loft. The big bag is also nice for stuffing your clothes in so you don't have to search for your socks in the morning. I bought this bag after I had already purchased the Lightyear 20 and realized it was way too warm for most of my adventures. Together these bags will work great for a wide variety of weather conditions while still costing less than a single high-end down bag.