My number one request is consistent phone and Twitter service. Dealing with a schedule change this weekend was frustrating with multiple calls and multiple excuses as to why my 6 hour schedule change shouldn't grant a free change.
Also, al a-carte dining in D1 with multiple options. Sometimes I just want a light salad it soup when getting on the plane and would prefer the heavier meal later on.
Twitter service, in my opinion, has gone downhill since it was first introduced. Though KLM's Twitter agents are even more useless.