DerakkonI have this chair (got it at REI back when they used to carry it).
It's great but its not the lightest option out there, I've been eyeing the Helix Zero myself(16oz vs 45oz). The Chair One is 33.6 oz. Aside from the heavy weight, this chair is very comfortable and its a little more of a reclined position whereas the One and Zero from Helix are more upright. I haven't had issues with sinking with the Mantis like some people have reported in some reviews.