"What can I say? I loved sleeping in this bag! High teens and low twenties at 13 K feet and all I wore was a very thin base layer to keep my skin off the bag, and I was sometimes too warm all night long. And it was quite roomy, while still allowing me to cocoon myself as needed. I had no cold spots, and was always reticent to get out of the bag in the morning (nature notwithsatnding).
I think I would be very comfortable in this bag at even lower temps if I wore some warmer clothes to sleep in. The other thing I liked about it is that the hood is so comfortable that I didn't need to wear a beanie at night at all. And my "pillow" also fit in the bag's hood easily all night long. I also had no concern for condensation on my bag (but realize we had very little to no moisture in our tent anyway (Haven 3))
I have some other bags, but I know I will be using this one predominantly in the future unless we will specifically be in very wet conditions."