I was actually trying to figure this out for myself a while back...
I remember actually sleeping in a hammock on a trip a few years ago before I actually new what I was doing and that you could even use a hammock as a shelter. I was on a trip to Wheeler peak, NM with my girlfriend (now wife) and her friend (also female). So we had 2 two tents and I'd packed in a Byer parachute hammock just to lounge around in. After we set up camp, I went down to pump water. When I got back I found the two girls lying head to foot in MY hammock asleep! Later in the evening I actually got a turn in the hammock, and after getting comfortable there, I wasn't looking forward to going to my tent. So being new to backpacking, and completely ignorant of anything lightweight (who ever heard of ultralight... I was wearing jeans for crying out loud!!!!) I also had packed in a blue walmart tarp, because I planned to have an area to cook under in case of rain. (So I'm half brilliant)
I strung a line between the trees and A-framed the tarp over it. It was the most comfortable night of the trip.I didn't think to use my pad in the hammock though. I remember being a little chilly. I slept in the tent the next night and was miserable. It's not even the hard ground that's the worst. It's sliding off the pad, and sliding into the wall. But the roots don't help much either.
I probably wasn't really thinking of it at the time, but I believe the first time I ever saw someone use a hammock was while I was in Basic Training at Ft Knox. We were spending a night out at the range firing the tanks, and about 30 of us wear sleeping on the floor of a small room. Not my Drill Sergeant! He strung a hammock up under the covered picnic tables outside. I thought he was hardcore, and believe me he was, but maybe he just knew a better way.
Hennessy way the first company I knew about and was dead set on getting one, until I found out there were other options through Hammockforums.net and Jeff's site.