Let me first say that I changed over to hammock camping about a year ago. I was on a group day hike in south Texas walking through a shady grove of live oaks. I mentioned to one of my fellow hikers that this would be a great place to camp and get out of the sun if it weren't for the thousands of football sized rocks everywhere. She pointed out that if I was a hammock camper that wouldn't be a problem. Suddenly the light went on. With a hammock, no looking for level spots, heck camped on 30* slopes if you want, over logs, bushes, rocks, roots, etc. So I gave it a try.
I was concerned because I am a side sleeper, but the funny thing about a hammock is that you are not confined to side or back like on the ground. You can sleep on you side or your back, but since a hammock supports your whole body you can also sleep halfway in between or at any angle you want. Very cool.
Speaking of cool, the under insulation is a real issue but is easily dealt with. I have a 15 oz under quilt that is good to about 35-40* for me. That is about the weight of my ground sleeping pad so weightwise it's a wash. Depending on which hammock I use I can come in at between 21 oz to about 32 oz for my shelter (hammock with bug netting and tarp and suspension) which is in the range of my beloved TT Contrail, so another wash. And yes I have practiced pitching the hammock on the ground as kind of a glorified bivy, so if I can't find trees I can go to ground.