Switching to Delta brings many pluses and minuses into the fold. One thing I have actively avoided over the past 6+ years will return when I make the move to Delta. In a word, Atlanta. If you've never flown through Atlanta, be grateful, but this is Delta's largest hub and the one in my backyard. Atlanta will be almost impossible for me to avoid.
Why do I hate Atlanta so much? It's not any one things but a combination of factors. When I lived in Wichita Kansas, my flights back from visiting family in New York, always routed me through Atlanta. There is not a single time that I returned from Wichita, that my baggage wasn't lost in Atlanta. That's right, 1-2 flights a year for 4 years, every single time. Granted my flights to New York never lost luggage, but the reverse trip never made my flights. Now I don't ever fly with checked luggage anymore, so I've managed to eliminate this problem, so while it was annoying, I've made it a non issue.
Second and probably most obvious to those transiting Atlanta is the layout of the airport. Atlanta is huge, and it take roughly a lifetime to get gate to gate out of different terminals. Atlanta is laid out in a fashion that allows great aircraft flow in and out, and really on the surface seems like a smart design. Right up until you have a close connection from one end of terminal B to the other end of terminal D or even farther. The terminal layouts mean you can spend 15-20 minutes just walking half the length of a single terminal. To get to the next terminal, you have to descend underground. Either wait for a tram or walk to the next terminal you need to be in, and then walk the length of the next terminal. This can mean in worst case scenarios, 45 min walks between gates or in some cases even worse. Add in an international customs clearance process and it becomes a nightmare.
I've so avoided Atlanta over the past 6+ years, that it will be interesting to see if the airport is anywhere close to being as bad as I remember it. While the layout seems smart on the surface, in practice this was my most dreaded airport.
Things might change here though, as I now have gotten the hang of minimizing my stress at airports. Using lounges pretty much all the time and generally enjoying my trips to and through airports. It may be a whole new experience with Atlanta... but we'll have to judge that in the coming months.