I have an M65 hammock which was issued to me. I used it in Panama years ago, while in the US Army and have used it on several trips since. It is very narrow, which is not a good thing. It is made to be used with a USGI poncho as the rainfly, the elastic toggles on the main lines are made to button into the large grommet holes on the poncho.
It is comfortable if you can remain relatively still and sleep on your back. If you can't sleep on your back and you roll about frequently, there is a good chance you can fall out of the hammock. I survived using it, with some loss of sleep. In Panama we learned quickly why the hammock was best pitched chest high. The rain was heavy enough that it bounced off the wet ground and wet the underside of the poncho and the inside of the hammock, unless you set the hammock up quite high. It was common for army troops in Panama to buy a net hammock to replace the nylon M65, it was lighter and also let air circulate better. The whole setup was heavily dependent on a good mosquito net, pitched carefully.
I've since bought a few other hammocks, and the one I prefer over any is the Ray Mears version made by Pyramid, with the RM bug netting and an Aussie hootchie for rain cover. It is wide and allows for a much more comfortable night's sleep.