I recently used the lightweight 40 non-hooded sleeping bag in the Black Hills. It got down to around 50 degrees in the early mornings. I was warm enough with it. One night I woke up slightly cold but realized I had moved off of my Ridgerest. Once back on the pad I was fine. I used it backpacking around the Harney Peak trail and it was nice because it was light and highly compressible. I don't sleep well in mummy bags because they are so tight, but this was roomy enough for me to get comfortable in. I am short (5'7") and if you were over 6' the regular may be too short for you. Overall, I loved it. Did everything I expected it to do without breaking the bank.
This review was written in the old system and had content requirements that are different than reviews written today.