Personally I find them pretty cushy. Especially when they are double thickness like this one:
The problem I always have is that I get insanely cold. What happens is that the air in the mattress tends to stay the ambient room temperature and to suck all the warmth out of me. However one of my roommates told me the way to defeat that problem. Simply put a warm blanket under you. Why didn’t I think of that?
So my go to now is a sleeping bag. A nice warm cacoon and the air in the mattress can just stay cold.