Hennessy is of the elite of hammocks.
Pros:
good quality
versatility
side zipper option
Having slept in a Mexican hammock for a few weeks straight on vacation once, I figured that I could tolerate one as a shelter. It is a tough call whether a hammock will work for you or not, you just have to try it. And you may also have to be very patient...it took several years before I finally had a real breakthrough with mine. I am generally a side or stomach sleeper, so it has been an adjustment for me.
After a lot of reading, I went with the Hennessy Ultralight Backpacker with a zipper, because of its reputation and features.
By the way, the hammock forums (Google it) will tell you all you ever need to know about hammocks. There is also a wonderful book/website on hammock camping called the Ultimate Hang by Derek Hansen
The zipper is a newer feature and one that was kind of a deal breaker for me...I waited for a bit until Hennessy finally started making these, as opposed to the bottom opening. But it does make it a bit difficult getting in sometimes, mainly because you have to hang the hammock pretty high at first to account for the stretch in your suspension. If you don't start out high enough, your bottom just may end up brushing the ground.
So when getting into the hammock from the side, sometimes you have to almost do a high jump maneuver (I'm exaggerating a bit). One must also consider the opening side when you hang the hammock...upslope as opposed to downslope would be preferable.
I have used my Hennessy only in Florida so far but the very first night out in it, the temp dropped to 38 degrees. I used a Therm-a-Rest, a reflective sunscreen for a car, and a 30-degree down bag, and I was just warm enough..thank goodness there wasn't any wind. On another night, I was too cold in my 40 degree bag, and I don't think it got below 55. I didn't consider buying the Hennessy supershelter mainly because I didn't anticipate using it in very cold weather very often. I have since found a much better solution in the Sierra Designs Backcountry bed and my Neoair Xlite thermarest. The backcountry bed has a pad sleeve that keeps the pad in place under me and the quilt-like features of the bed allow for easier entry and exit that an zippered sleeping bag. The Xlite also has a much better R value than the old thermarest I was first using. If I moved to using the hammock in colder weather, I would get an under-quilt.
I have also replaced the stock suspension with whoopie slings and Dutchware bling, which makes a HUGE difference in functionality and set-up times.
Lastly, the supplied tarp is quite small (some call it the Hennessy napkin) so I have also bought a tarp with more coverage, along with a ridgeline for hanging the tarp
