Hi Uli,
I also experienced some flights on KLM with bad service and not to clean Lounges. However I also had some of my best flights on KLM. I ussually found the cabin crew very attentive and friendly. Sometimes I got a level of service superior to some airlines First class, sometimes I was told "If you like coffe you can have the old one from Amsterdam or you have to wait three hours to breakfast ..)
Whereas LH is very consistent on KLM there seems to be more variation, but donīt give up, sometimes they can be really nice ...
Thomas