My experiences (typically 2 or 3 long haul j trips a year):
Food is not great, most of the time but can be good once in a while.
The lounges in Amsterdam and at outstations are horrible. Relative to a lot of other business class lounges out there, they are almost unacceptable. This applies mostly to the non-schengen lounge which I'd assume is used mostly by long haul premium customers, and lounges like the AF/KL one at YYZ. The Schengen lounge at AMS isn't bad for short haul trips but is also super crowded.
Wine and liquor options are not too good either in the air or in the lounges.
But the service has been consistently very very good.

It's not bad overall but it never feels as luxurious as J on some other airlines either. That said many airlines have their weak and strong points
BA seats are awful but I tend to like their booze options in air and on the ground; US airlines typically have poor service but DL for example has fleet-wide lie flats and direct aisle access, UA and AA are rolling out some pretty great lounges for long haul business; etc.

KL needs to do something about the lounges, food and drinks if you ask me. But I'm not holding my breath