Pros
Citadel attracts smart and ambitions people (not necessarily nice, humble and easy to work with), by lying during the interview about career prospects, the job description and their "amazing" technology. Most people will eventually realize that this is not a good place to work and move on, as a result citadel has the highest turnover rate of any finance company. This creates a very volatile environment.
Cons
It is very unhappy place to work. The employed are needlessly stressed, harassed and burdened with busy non-productive work. The work at citadel is a constant struggle with legacy technology and management. The primary focus is to produce a lot of mediocre work instead of building something exceptional. There is no work/life balance, you are expected to work at least 12 hours a day and be accessible 24/7. The technology is desperately outdated and they resist any progress with almost religious zeal. People are resigning at the alarming rates, and company frantically tries to hire just to keep up with resignations. In order to speed up hiring they resort to outright lies, deceit and dirty tricks. Make sure you carefully read what you sign at citadel (consult with a lawyer). Because of the high turnover no one in the company knows anything about the "system", you cant ask anyone anything because 1/3 of people you are working with were hired last year. The rest are completely discouraged from doing anything productive and actively looking to quit. No teamwork.