DTape,
I've made and used a "hammock sock" and measured a 7degree F difference between "inside" and "outside".

For everyone else (just throwing in my $0.02)
My winter sleep system is the same for tent or hammock:
3/8 CCF pad, Exped7 downmat, RayWay Alpine quilt, 100wt small liteweight blanket to cover the ccf pad, appropriate sleep clothes depending on temps.

My hammock/tarp is slightly lighter than my tent, but I don't hammock due to weight. I do it for comfort. The pain in my shoulders when sleeping on the ground is excruciating. In a hammock, I have no pain.

My lowest temp has been 22F with 35mph winds. We don't have snow down here, just ice. I've done ice too. If I had snow, I'd try both a hammock and a tent and see which I liked best and go with it.

As for Shug and his video's, he is always testing gear!