When it was truly AT&T customer service wasn't bad, especially for business customers, but when Cingular bought AT&T they adopted the AT&T name but kept the "stellar" support that Cingular was always known for.
I also never had any problems with Cingular. Perhaps it is a regional thing? I live in a former BellSouth Mobility PCS (GSM) market, not SBC or PacBell. When I need something I call them and get it. If I feel like talking to someone in person, I just go to an AT&T corporate store, and everything works out fine. This has also been the case for my parents who have had a similar experiences in Jackson, TN, Myrtle Beach, SC, and Oneonta, NY.
From my perspective, DirecTV CS seems about the same as they always have been, which is better than TWC/Spectrum, Frontier, and Verizon (other other telcos I deal with), but not as good as Dish.
As a business customer, I found AT&T wireline and business fiber internet CS to be terrible. The sales people always blamed it on the union, but the techs told us it was the sales people selling things that didn't actually exist, and then engineering having to make it happen somehow. I tend to believe the latter as I've been in that position. The results are always hard or impossible to support. Ironically, I couldn't even get an AT&T POTS line for a fire alarm system in a new building in downtown Raleigh, NC, literally right across the street from the big Central Office.