I got to put my Potomac to the test last night, really for the first time.
There was little to no wind to speak of, but it got down to the mid twenties where I was. I had no idea that it was that cold until nature called very early in the morning and I had to get out to take care of things.
I didn't have the quilt in "cold mode" either. I just had all the shock cords pulled pretty tight and it worked perfectly.
I'm completely satisfied with the Potomac. I'm all but certain that I could take it down to 20 degrees without adding any insulation to the hammock system, and it's probably my favorite gear choice since I dumped tents for my hammock.
Here's a photo: