Once you are balanced, it is fine and you stay up with little or no effort. It also sits flat on the ground and provides back support if you would rather not balance.
I have one of the therm-a-rest chairs. They are nice, but I like the one in this thread better overall. Although if you take out the pad in the therm-a-rest chair it is about 1/2 the weight.
I think I went through about 4 portable chairs before I landed on this one.