And, I got my $50 discount! I was hesitant about getting a bed I had never tried. And I really, really liked the Simmons beautyrest Legend McFarland that was over $2000 for the XL twin - but I was going to be able to get a large discount. But I remembered your advice, Phoenix, and decided to go with the $700 (after discount and free shipping) OSO. So comfy - honestly, as good as the Simmons and will probably last longer and be less toxic. I really like the slight contouring and almost a little “bounciness”, just a little for comfort - and yet still very supportive. More importantly, my son loves it - even more than his pricey mattress at home! Honestly, though, I am not sure I would want this for a shared mattress. If one sleeper was a very different weight than the other, it might not provide the stabilization, so to speak. (My Harmonia is great for this - dh can toss and turn while I am sound asleep!)
A few comments on the total experience: I called the support group at OSO for shipping advice, and they gave accurate estimates of shipping dates and deliveries. The mattress was perfectly packed and only needed about 1 or 2 hours to de-compress. It was odd - an XL twin is supposed to be 80 inches and this was about 78 or 78.5, which is a bit strange.
Thanks again for all of your help!