I bought the 15 degree UL super down spiral last week. Got a great deal of $369 to my door by calling the Mont Bell warehouse. It is last years model which I'm told is essentially the same as this years. This bag was recommended to me over the WM Badger because of the design of the bag. I have not sleep in it yet but laying in it at home I am very impressed with the bags ability to stretch and move with me. I can stick my elbows way out and also stick my knee out as I lay on my stomach. Very cool bag. It should take care of that mummy feel that comes with these type bags. Freedom of movement is amazing.
I am a stomach sleeper and like to spread out, and so my Montbell Super Spiral 30 degree down bag is the most comfortable mummy type bag I have ever slept in. I was always uncomfortable in the military in the ?10 lb Military 2 mummy bag/1 bivy sack sleep system when it got below 45 degrees and had to actually zip it up. The only thing possibly more comfortable for me so far for winter camping is using two big square 5 lbs each car camping bags with one cinched around my neck tightly and the other loosely covering my head to create a warming chamber to breathe in.
I have my bag in a Montbell sleeping bag cover and use a Sea-to-Summit liner so I don't ever have to wash the bag, condensation off the Tipi can't get the bag wet or if I want to bivy with just a poncho shelter, and to protect the bag's very thin/lightweight materials. This whole set-up weighs 37 ounces and I have slept down to 12-15 degrees comfortably with my fleece hat on on a couple of occasions. My wife who is a much colder sleeper than me has the Super Spiral Burrow Synthetic 30 degree bag with Sea-to-Summit silk liner and has slept comfortably at 15 degrees with her base layers on.
I have the 30 degree super spiral hugger with 800 fill goose down. Im a warm sleeper and I hope I can take it down into the 20's without anything, and I might add a sleeping bag liner just so I don't have to wash the bag as well.
I got a UL SS Down 15 degree about a month ago used it a couple times and love it. I also got the montbell bivy and I can fit my neo air xlite inside. I use a sea to summit liner as well and being this is by far the most comfortable I have been in a mummy bag.
I've always found the Montbell bags to be a little optimistic with their ratings. The 30 degree bags are more like 35-40. In fact, I just read somewhere that their new bags finally are EN rated and they had to add a few ounces of down over past year's bags to make the new bags meet their target warmth ratings. So, apparently they're now more accurately rated, but also a few ounces heavier.
First impressions of my Montbell UL Super Spiral 3. This thing is roomy. I'm a very large person, 6'4 260 lbs and very broad up in the shoulders and its the first sleeping bag I don't feel cramped in. Its plenty long enough for me to tuck my head in and use the cinch strap. If you're a bigger guy and you want to get a lightweight bag that you won't feel like a sardine in give montbell super spirals a look. If I can fit in the bag and not feel cramped 95% of guys will too! The bag weighs in at 1 lb 8 oz's and comes with its own stuff sack. Even in its stuff sack its very compact and then unfolds into this HUGE BAG! Great purchase and I'm very happy, if you're in the market for a down bag give montbell a look.
I have both the superstretch UL #1 & #3. I am a bigger guy and have always hated mummies due to the feeling of confinement. Montbell did away with that for me with the elastic qualitites built into their bags. My bags were from the last year before the spiral design came in about 2yrs ago or so. I sleep much better in these than any other bag I have ever used. I have found the temp ratings to be accurate for me and down to lower if I am using an insulated pad. I am a warm sleeper though for what it is worth.