Generally, DL CS has treated me really well too, hence the reason I fly them, but they are not perfect. I have some recent examples of outstanding customer service, including my last flight, but also some real doozies. DL can be very inconsistent, and as much as you fly, I am sure you have run across this. I have learned not to take anything for granted. If I have any chance at an upgrade, VDB, standing by for a flight, etc., I am always near the podium when the GA arrives and check in at the podium a few minutes later with an innocent question. If it looks like I will clear, I might request a specific seat assignment or if it looks accurate that I will clear, or if I am a few down, if there might be any no-shows or misconnects that would open up a seat for me. Its unfortunate that this is how the game must be played, but these days, you have to put in a little extra effort if you want the benefits you are entitled to.