Pretty sure I had one of these on BGI-ATL back near the beginning of the year (was definitely a 737-800 at least, and the inside was very definitely pretty old). Not in first class, and quite frankly, I found the seats to be pretty excruciating. I'm not even sure I'd say it was better than the 737-900's to be honest, and yeah, those suck. It was one of a few things that contributed to me almost being unable to stand because my back ended up so bad the next day (in fairness, it wasn't the only contributing factor, but was more like icing on the cake after spending a couple weeks on a very uncomfortable bed).