Just had the full Casper deal on AA193 LAX-HKG. I think it's almost *too much* bedding, I could do without the lumbar pillow and thin blanket. But everything else was good and made the flight more comfortable. While the materials are still a bit rough/coarse, I found the duvet to be warm but not too warm, the mattress pad decent (could still feel the breaks in the seat but helped), pillow even good enough for side sleeping (but maybe too firm for back sleeping) and the slippers and PJs welcome.
While the PJs won't win any fashion awards, and the material not super soft, they were good enough and the pockets useful. I was not a fan of the elasticized cuffs at first, but later appreciated them as they kept the sleeves and pants legs from riding up. I found the S/M size to still be on the large side so it will be a baggy fit in general.
All-in-all, an improvement and I think better than what UA Polaris sounds like it's offering.