Pros
I have been with AT&T for over 30 years, through several name changes. I am not going to sugar coat it, if you are willing to work and adapt it is a great place. If not, look elsewhere. Benefits are good, pay is good. It is a large company, so it has it's challenges. Education is valued and tuition aid is available. There are opportunities for advancement within the company. I have friends in other large companies and comparing their experiences with mine AT&T is as good an employer, if not better than most. In my job function I work in all aspects of the network (wireline, wireless, data etc.) so I have a fair knowledge base.
Cons
Sure there are cons just like any other company, but they are petty ones not worth listing. I know this a one sided review, but I have a great career and honestly wouldn't change a thing.