There seems to be a very mixed response here. I use KLM frequently, in both WBC and Economy and, while I cannot get excited at the prospect, there is little to complain about either. Luggage and connections are normally reliable too, Amsterdam is very user friendly and KLM prices usually undercut most other options in all classes. The entertainment system on the 747 is a real downer in economy but on the 330 (my next trip in economy) it is seatback.
Economy Comfort is automatically given to Platinum Card holders at no extra cost – its not a discretionary upgrade. Others have to pay but not very much. That’s important because Economy Comfort is NOT equivalent to Premium Economy on the likes of BA or QF nor is it intended to be. The additional cost over Economy is marginal compared to BA and the like.