I have one and at first it was great. Stayed warm down into the 20's but the more times i have used it the worse it has got. I am cold sleeping in in the mid 40's now.
I have used mine twice so far since I got it a few weeks ago. It was high 20s and i was sweating in a base layer. I’ll update as I use it more but can’t complain for the price it packed small.