Your one bag quiver!
This is absolutely the best bag I've ever owned. I still have a 0 degree bag that I bought at REI 2 years ago but have not used it once since I bought this. I've slept in this bag down to 10 degrees and with a hat on my head and a baselayer on I slept like a baby. I'm a cold sleeper too! When push comes to shove I'm sure it wouldn't be comfortable, but in a snow trench and a bivy with all my insulating layers on I'm sure I could handle 0 degree temps in this bag, and all at a pound and a half (regular)!!!!!
I've also slept in 50degree temps using this bag loosely draped like a comforter. It breathes really well and if you're willing to lug an extra half pound you can save yourself 400 bucks for a lightweight down summer bag too!
I can't say enough good things about this bag. Worth every penny and making the bomber reputation of WM even better.