Hmm... I am very tempted to make use of this offer. I usually book Eco Comfort. The price difference between that and Premium Comfort for the date I am looking at isn't too much (120 euro). I am looking at open-jaw tickets AMS-ORD & SFO - AMS. So with the cashback a 'no-brainer'. However, KLM doesn't offer Premium Comfort on the AMS - ORD flight (operated by 777), only on SFO-AMS. Wondering if it will register correctly if I book Eco(+) on the outbound, and W on the return... the small print doesn't say anything... it is still 'trying out Premium Comfort' even if only upgrading one leg.