Pros
The work environment is very flexible and casual, and the hours are not as long compared to other Citigroup or finance jobs. A generous amount of vacation is allotted even to new employees. There are a lot of smart employees and you will also learn something from everyone--even a junior fresh out of college. Employees come from various backgrounds and industries, and that makes for a good diverse environment as well. Because ATD is an electronic trading firm first and foremost, traders treat technology people with mutual respect and don't look down on tech people. For technology professionals in Charleston, SC, this is THE best company to work for.
Cons
The business unit is really limited in its role by Citigroup in NYC, and due to politics, inter-team relations on site can be quite difficult. VPs and team leaders prefer to keep their heads down and lay low. ATD also recruits with the image that they are the old ATD before the Citigroup acquisition, but all of their marketing in that respect is a bit misleading. That "small" company feel is gone, long gone, and it can be depressing listening to people who where at ATD before the acquisition talk about how things have changed. You will always be a bit of an outsider to them as well if you weren't with ATD before the acquisition.