To be honest I've always avoided Chair kits because I didn't want to risk puncturing my sleeping mat - somehow it seemed a bit brutal to fold it up then sit on it and you can always sit on a rock - can't you? While preparing for my last trip though I was persuaded to take the Sea to Summit Air Chair Kit as a test item, I tried it before we left and it was just too comfortable to leave behind, besides my mate was taking one!
At 228grams its a significant weight these days but if it worked the access to a padded chair with back support was well worth it. There are slightly lighter chair kits available but what I liked about this one was that the nylon panels cover the base of the chair thus protecting the mat a little better than the lightest versions. I also carry a foam sit mat for sitting on cold lumpy rocks at lunchtime, when using the chair kit I also placed it on the foam sitmat as further protection.
Folding and fitting the mat into the Chair Kit can be quite fiddly, the mat should be slightly less than fully inflated for best results. Once the chair is setup its extremely comfortable, and after initial careful use I was soon flopping into it and leaning back without thinking, being 15stone this put quite a bot of force on the chair which it handled without a problem.
Using the chair was a revelation - after setting up camp I would put the chair together and sit down, from my lowly perch I could do just about everything I needed to - first was a cup of coffee, later I'd cook from the comfort of the chair, I could sort the tent out and take care of any gear repairs or whatever. Because you set the chair where you want it - usually in the tent doorway - you have access to all your kit, this is in contrast to sitting on a rock - which is invariably set away from your tent meaning you have to get up to do things.
You don't have to use a Sea to Summit mat with the Air Chair Kit - my mate used his with an Exped Synmat 7 UL - its a bulkier mat than the one I was using so it required a bit more fiddling to get it set up. The Chair kit I was using performed faultlessly throughout the three week trek however the stitching failed on Geoff's kit making it tricky to use properly. Mid way through the trek we managed to get it restitched and it was fine from then on.
So, I've changed my view - I won't be leaving home without one.