I've been a backpacker for several years and am not slowly transitioning to more car-camping or "overloading" as I get older and slower. I swapped from tents to hammocks about six years ago. My primary seasons for camping are fall and winter (I hibernate in the summer because it's too damn hot out). Coldest I've seen in the hammock is single digits (F). With a proper set of quilts, clothing, and a Nalgene bottle full of hot water you can be warm and cozy. I tried using a pad in the quilt and it's just too clunky for me. The underquilt is far superior. I do have a tent and 4-season pad for trips where I am above treeline but i sleep much better in the hammock.
I just got a 4Runner about a month ago and am impatiently waiting for fall when the temps drop below 70 so I can get back out into the woods. I plan to rig up one end of my hammock and tarp the roof rack. Curious to see what sort of tarp coverage can get along the side or back of the Runner to give myself some rain coverage while still being able to access the inside of the truck.