Pros
ATCC has a very laid-back work environment. There are excellent benefits and you definitely don't have to worry about job security here. The company has a great reputation (from what I've heard from people in the outside world). I've met some great people here and overall most are great to work with(not including supervisory/manager positions).
Cons
Due to the company restructuring, it is nearly impossible to get a promotion. There is no room for career advancement at all. Favortism runs rampant here within certain departments which really effects the morale of the employees. The people here who work really hard are often overlooked and expected to clean up the messes of the employees who could care less about having their job. Higher level education (not including a doctorate degree) doesn't mean much here. Having a M.S. here doesn't affect starting salaries, it only counts as a couple of years of experience when trying to get a promotion.