I'm a hammock camper. Any old hammock will do, but the trick is staying warm. When you sleep in a hammock, the hammock fabric compresses the insulation (your sleeping bag) and basically removes any insulating properties. In order for your back, butt and shoulders/arms to stay warm, you'll need to figure out a way to prevent your insulation from being compressed. There are two ways to do this. You can 1) use closed cell foam or 2) put the insulation outside the hammock. i prefer #2, and I use an underquilt that hangs beneath my hammock and insulates me from my shoulders to my butt.
I will say that the way you insulate the hammock is far more important than which hammock you choose.