i just got back from a 3 day trip up in the hills over the long weekend. i have a ENO hammock, and i brought it just cuz, not necessarilly to sleep in for this trip, however my dog got a case of the stupids and started fighting with me the first night over my sleeping pad, dog got a swift kick after he popped my ultralight air matress.... needless to say that hammock saved my bacon.
i love it, the only downside is that there isnt any insulation under you, so either dress warm and hope you dont sweat in your sleeping bag, or just have a synthetic bag. i have a down ultralight bag, and while its provided many warm nights, its not ideal for a hammock
interestingly enough my buddy has the same one, and he found that a US military surplus poncho stretched corner to corner with the hood tied off well, provides an excellent ultralight shelter
like anything it has its drawbacks.....
nothing is worse than trying to fumble for your bags zipper at 3am cuz you gotta take a leak and spend 10 minutes fighting with it while trying to not end up on the ground
other than that, they are awesome