From my personal experience I usually get e-mails answered within 24 hours, some difficult questions it sometimes take two days, but overall very good communication. On the phones I never have to wait more than 30 seconds and some FAs are really good about taking care of Medallions, but it depends on the FA. I have received drinks comp'd, free M&Ms (the ones they usually charge $2 for) and one FA came to my seat during a transatlantic flight thanking me personally for flying DL. So I'm pretty happy with the treatment.