Pros
Jump invests in it's employees as if we all are going to stay with the company for decades. Which is what many of us plan to do, as long as one's trading team stays profitable. Examples speak better than words: 1. Almost any data set is available internally, and catered lunches and a lot of company-arranged events make it so that different trading teams know each other and talk and cross-pollinate data, ideas and even technical tricks (the latter is very different from most Jump's competitors where different trading teams are secretive and don't share), 2. Jump pays for all sorts of internal trainings (I took Advanced Python and one of big data classes, planning to take FPGA class next) 3. I saw two teams dissolved for bad performance this year, however almost all of the former employees of those teams... ended up joining other more successful trading groups within the firm, internally
Cons
Structure is very flat, which could be viewed as a disadvantage. For example, if your idea of career growth is to have important-sounding job titles and promotions every other year... that's not going to happen! Instead, as you grow within the company you'll get to mentor junior colleagues and/or play with increasingly more sophisticated technical "toys".