"This is a stellar, inexpensive bag that easily meets the needs of any three-season camper."
I got this sack because it was the cheapest down bag that I could find; it was well worth the price. I wasn't expecting anything for below freezing weather, but I made it through a frosty night semi-comfortably sleeping in this. With some long johns and a little layering, this can get you through some chilly nights between 30° and 40°. It's extremely comfortable, and you just let it wrap around you. It can easily be too warm if it's near 60°, but just use the zipper and sleep naked.
There are definitely better 40 def bags out there, but you will be hard pressed to find a down bag in this price range. Took it on two trips so far and it worked great. On high camp in Olympic NP, it got down to around 40 at night and I was just fine in some long underwear. On the coast - more than enough. Above 60 it gets too hot and I was crawling out of it. Zipper seems OK to me and there is reasonable wiggle room for a fit person. Best part is that it is down, so it compresses very smal. This will definitely be my go-to bag for lightweight above freezing camping.