Pros
Company strives for high standard in leadership. Expectations at each level extremely high. If you make it as a Director here, it means that your scope and span of work is huge. A director here can have as much challenge and responsibility as VPs or SVPs in other companies. Same for higher levels. Att is really a lean company for senior management and has few leadership opportunities.
Cons
The culture is so old fashioned, they are trying their best, but it is hard to move a company with hundreds of years in existence. There are a lot of Christians who happen to be leaders in the company and tell others their religion views and conservative notions. Beware. if you happen to be progressive or liberal. Promotions are hard to come by and they pay so little!!!. I know because I worked in HR and know how they compare with other companies. Very inflexible, change takes a long time. And for all the development stuff that they have, I wasn't impressed with their talent level. because talented people will leave a cheap and boring company.