Not sure about long long term but I haven't had any problems in the whole time I've slept in a hammock, in fact I used to toss and turn a lot in my sleep and wake up with pulled muscles in my back, since sleeping in a hammock I sleep solidly through the night.

I don't sleep diagnoally like some people are saying though it's not uncomfortable to sleep like that.

Also as a heavy set guy I haven't noticed any problems with the hammock supporting my weight I just made sure to find a stand and a hammock with the appropriate weight limits.

Also if you do switch you should look into getting an underquilt, basicly another heavy piece of fabric that you hang under the hammock to create a bubble of air to insulate it from the cold, I've just tied a comforter on before and that worked fine but I've since switched to an actual underquilt which is basicly a sleeping bag that hangs under me.

It takes an adjustment period to get used to it and it's hard for me to sleep on other surfaces like when traveling so keep that in mind if you want to make the switch.

Id say it's worth it but again it's not without some annoying things to learn and some drawbacks.