Before this devolves into much more a shouting match, let me clear something up. If you are going to argue about what works best, you have to consider the same place and same conditions.

Winter does not mean the same thing to everyone on this site. It is not just a season or a temperature rating, it is a set of conditions. What Eric is talking about is snow on the ground winter, where the possibility of snowfall is likely, not just cold temperatures. Big difference.

Lori is right about apples and oranges. Keep in mind that a lot of winter camping is done in areas with no trees. Look at some of Otto's pictures from Norway and Sweden - no trees in sight. There are no trees in a lot of places people winter camp, so hammocks are not feasible just for that reason alone.

Personally, I would not want to be in a hammock in a snowstorm or in high wind, but maybe that works for other people. For me, a hammock is too claustrophobic. I use a two person tent, which you can see in my trip reports and that's just for me.