I haven't used them but was on a trip where they were used and in that scenario, generally worked well for individuals.
The scenario was on a 2013 supported ride across Africa (TDA). It was a supported ride, so people didn't carry that gear - but were limited to a fixed "locker" space. The cots they used folded pretty nicely and small for this space. The lowest temperatures we had in the entire four month trip was 4C/39F on morning in the Ethiopian highlands so warmth was not a big issue.
I used a thermarest. The problem I had, as did most of fellow thermarest users was that we went through areas with a *lot* of thorns. We pitched our tents in a general common area and even when one tried to be extra careful, with ~100 nights on the ground it was pretty easy to end up with a small puncture. I brought a patch kit and patched at least two holes in my first mattress and later bought a different thermarest from someone only on part of the trip. However, still had some nights ending up finding a deflated mattress.
So for that trip at least, and for those scenarios, I would recommend a lightweight, small foldable cot.