I've flown on some lightweight seats with Lufthansa on a short haul flight recently. Even on a 2 hour flight, they were the most uncomfortable airline seats I've ever sat in. The seats were very thin, padding was practically non existent & the experience was more like being sat in a waiting room chair. If I knew the seats when I booked then it would influence my choice of airline. So, think we won't notice? I'm not so sure.