When I heard that a friend had bought one of these for a week long canoe trip we were going on I thought it was absurd. The idea of taking such a home comfort on a camping trip went against everything I felt camping stood for. Then I tried it, then I bought one, now I take it on every camping trip I make.
It's so light it adds basically nothing to your carry weight. It takes seconds to put together. It's insanely comfortable. Kicking back in it after a long day's hike or canoe whilst prodding at the camp fire is such a joy.
I put it alongside my thermarest as a thing I never felt I'd ever buy and now use on every trip.
Definitely worth having something other than the ground to sit on after a long day. I have a couple of light weight 3-legged stools, although they likely wouldn't be considered ultralight, that are light enough for the camping and hiking I do, although you have to sit just right to not crush your balls.
The Helinox Chair Zero is the standard by which all backpacking chairs are compared https://helinox.com/products/chair-zero - and it is 1 lb 1 oz.
And then some people mod these chairs, like this similar one that was reduced to 13 oz. https://backpackinglight.com/forums/topic/chair-enlightening...