REI Halo +25

Ultralight under 2lbs, packs down to the size of a six pack, and kept me beyond warm in 20 degree nights.

So it weighs less than 2 lbs vs my 5.5 lb synthetic and packed to about a quarter the size. I had been cold in my 0 degree bag on 35 degree nights, but the Halo +25 kept me warm when the temp hit 21 degrees last year. And I mean comfortable, great sleep warm, not just survivable. I could feel the cold air against my face, but my body would've never known. I feel like I could take on 10 degrees or lower honestly. The materials this bag is made of has got to be the most comfortable I've ever felt. Silk like qualities. 

I should mention I use an insulated air mattress because if it wasn't insulated, I would've surely been cold as the bag would be compressed underneath me leaving next to no insulation on top of a cold air mat. If you don't insulate underneath you, you will never stay warm. 

The only issue is that I wear black fleece and I always end up with tiny down pieces all over me. haha. It's not enough that it would ever mess with the bags temperature rating or anything, it's just there. I liked this bag so much that I bought the Halo +10  for this season so I'm pretty stoked to see how it works out.  I would recommend this bag to everyone...

I've used it around 40 nights and never needed more. Warm nights I just leave it unzipped, as it gets colder, that zipper makes its way up.