Delta is just like any other big corporation. They pretend they care about you, but they really don't. A few middle managers and chief pilots are good people though and will help out where they can, just don't count on it.
As far as the pilot culture goes, it's similar to other airlines. 99% of guys are great and easy to get along with. I've been here 5 years and only have one guy on my no-fly list, and to be honest I'd probably fly with him again if I had to, I'd just rather not.
Most people here just want to fly their trips with minimal fuss, get along, and go home. You do have your typical share of over achievers. There's maybe a little more mission-oriented get it done attitude amongst the older Real Delta Pilots here than some other airlines maybe, but I'm just going off of anecdotal stories from my friends at other major airlines.
But overall it's a good place to fly, good people, and good CRM for the most part.