I'd love to try a Hennessy Hammock. It just sounds so much better than trying to find a place to sleep on hard, rocky ground, sleeping pad or not. But up until this point I just have lacked the nerve to try. And, well, there are practical considerations. My favorite camp site of past few years was just below the 6,000-foot level near Marmot Pass in the Olympic Range. No trees there, so its hard to hang a hammock.
Barring a lack of places to anchor the hammock, though, why not? They are light (2 pounds 12 ounces for the Expedition model, which runs $140), reasonably weatherproof, and generally easy to set up.
I don't know what the hype is. Mainly, you dont have to worry about finding a flat spot for a tent. Trees, on the other hand, are pretty easy to find. That "hammock" feel will take some adjustment, but most people can manage it. The biggest drawback? In cold weather you are sort of suspended in mid-cold-air. So you may need an extra insulating pad under you.
In warm weather they are great. You're up in the breeze, ventilation is first-rate, and they are bug-proof. Sweet!