I'm relatively new to hammocks, but have slept quite comfortable in -7ºC since and had the best camp nights i remember, and i've been camping since i was 2 month old.
I use a cheap nylon "coronel tapioca" hammock with a wool blanket and a poncho as underblanket, with a 3x3m tarp on top.
Being aware of the thermal process, the change from tent to hammock was not only easy but a pleasent experience.
I had read about this forum from the bushcraft forums and finally decided to join.
Will be reading the posts to try and catch up.