9W flights in AMS are handled by KL staff, many of whom are extremely disinterested in their jobs, are unhelpful and etc. When I fly KL, I encounter none of the issues I've had flying on 9W, from AMS to YYZ, just a couple of days ago (seat assignment issues, nitpicking on an extra kilo of luggage and demands to move things to another piece, etc).
Annoyingly enough, being a Delta PM means nothing, as they are not SkyTeam, yet Delta sells tickets on their metal - go figure. I may try it again in J, but in Y I think I'll pass...