I picked up the MontBell Spiral #1 before a couple of trips totaling about two weeks this September, and I couldn't be happier with my choice.
I was camped at about 11,000 feet in Colorado on both trips, and nighttime temperatures ranged from just above to below freezing. While MontBell lists this as a 15* bag, its EN comfort rating is 25*. on one occasion the temperature dipped to the upper teens and I was more comfortable wearing a puffy jacket inside my bag. The bag has continuous baffles, so depending upon conditions you can shift the down insulation from the bottom of the bag where compression means it provides little insulation to the top, or vice versa.
I debated between the Spiral and the Super Spiral based upon the dimensions, and I wound up selecting the Spiral based upon weight (4 oz lighter) and cost. The Spiral has plenty of room for sleeping in almost any position. I am an active sleeper, and combined with an Exped Synmat UL7 I comfortably slept on my back, sides and stomach. I could cross my arms over my chest, or pull up one leg into a "figure 4" position. I am 6'4" and the long Spiral which is rated for 6'4" max (compared to 6'6" for the Super Spiral) was plenty long for me.
All in all I would highly recommend this sleeping bag.