Rating: 4 / 5
I ordered the Vireo in a size Long with Quantum fabric and down overfill. Mine weighs 18oz. I've slept comfortably to 30 F without any supplemental insulation (wearing base layers and a hat) but I sleep warm. I've slept to colder temps (20s) but I was wearing the Hyperion jacket I bought at the same time to go with the Vireo (at a 15% discount if you order at the same time). I really like the bag and ordering in a Large allows the bag to come to my shoulders (I'm 74" tall) and I can seal off the bag with the drawstring. My only complaint is the girth of the bag from my knees to my hip is way too narrow. I compress the down from my thighs up past my hips/butt. It's quite constricting.
I used it a number of times like this but, with the inspiration of the BPL MYOG articles, I've now sliced the bag open and modified it into a 'arc'-style quilt. I certainly freed up the room around my thighs/hips!
So, it's a great bag but beware the narrow girth!