Pros
Big name on your CV. You'll learn some stuff and will open you good professional exits.
Cons
Horrible toxic culture fostered by toxic people. Arrogance and petulance are the law there. A culture of extremely long working hours completely out the legality. HR just close their eyes to the serious problems in some teams. As one manager put it once: "we are a huge red flag for HR and they don't even want to know what's going on here". Completely inverted pyramidal structure: for every junior you have 3 or 4 managers. Some managers on the team have more power than others and their decisions carry more weight which leads to an environment of management by terror and continuous brown nosing to satisfy their whimsical egos. Work is not valued: juniors do the bulk, managers get the bonus. Forget about claiming your overtime: having it recognized depends on how big the manager wants his bonus. Lower overtime on the worksheet=lower cost = appereance of efficient management= better bonus. Partners are clueless, they say one thing, managers do the opposite and as they are the ones closely monitoring the teams, they are effectively imposing their will over partners' directions. Partners are almost never at the office, only come to read the report before sending it. People are fired for personal reasons and HR doesn't step up since the are terrified to open the sewer cover. Sect mentality, your whole life is expected to gravitate around the office. Not spending time out of the office with your work colleagues can be seen as an offense in some teams. Firm's management tries to compensate the horrible office culture and low morale and very lo compensation with imposted social events. Here monkeys, have some peanuts and work harder. Trainings are absolutely useless and perfomance evaluations are rigged. No matter what you do, you can get fired for silly reasons.