A few years ago I purchased what had turned out to be my dream sleeping bag (in this temp range), a Sea to Summit Traverse XTII. The bag was light, compressible, warm as hell, had build quality like no other, and was an all around dream. I comfortably slept into the single digits with basic Icebreaker base layers and a beanie paired with an Exped Downmat 7 (I am a warm sleeper). About a year after purchasing the bag I had a change in employment, which put my wife and I on opposite schedules, so I sold the bag to pay for gear to better accommodate active pursuits that fit our scheduling (cycling).
A few months ago I got a new job, which put us back in sync and I started the pursuit of reacquiring gear. Being a little more limited in budget, I patiently waited hoping to find a deal on another XTII. Luck was not on my side for the XTII, but low and behold an opportunity presented itself for the Talus TSII on Campsaver. I couldn't be happier. The loft and quality of this bag is fantastic. It has more loft than my wife's "0F" bag! It is essentially a lighter and trimmer version of the XTII IMO. The bag compresses to virtually nothing (for a 15F bag) and the S2S zippers are better than with any other bag I've come across (Marmot, Mountain Hardwear, etc.).
All praise aside, this is a mummy bag through and through. I'm 5' 8", 170lbs and this is a comfortably snug fit. If you are much larger than about 5' 10", ~190lbs or move around a lot in your sleep, I would look elsewhere. I can comfortably sleep coffin/mummy style on my back through the night without issue, so the bag works fine for me. If you need a bit more room to move around or are somewhat claustrophobic, check out the XTII.
Let's face it, these bags aren't cheap. When you're talking about temps below freezing though, do you really want to gamble with a bargain bag?
This review was written in the old system and had content requirements that are different than reviews written today.