I used to use a Hennesy Hamock in the High Uintas of Utah (10,000 + feet). I absolutely loved it. There was quite a learning curve though. Many cold nights before getting it dialed.
50º Weather - Put a sleeping pad inside my sleeping bag
40º - 50º - Put sleeping pad inside my sleeping bag, and wrap an emergency blanket around the outside (I used to put it inside the hammock, but it was too noisy) I later switched to a fabric emergency blanket that didn't make noise.
Anything below I do all of the above, but then I take the rocks from my fire ring (that hopefully are really hot by now) and pile them under the hammock. I can cook in the middle of a snow storm it's great!!
Now a day I use an MSR Hubba Hubba while backpacking (I bring a dog or two).
Now for Overland/Car Camping and exploration, I'm using a nice springbar setup... Not ideal for a quick setup and move. But if I'm staying in the same place for a few days... I couldn't ask for more.