Pros
Close development on personal issues and how to improve personal profitability. Ability to develop your own systematic strategies on own accord. Encouragement to increase scope for profitability. Colleagues are in same position, drives hunger to succeed. Profit split is favorable to trader in most cases. You can use this as a platform to develop your CV for future hires. Ability to develop / improve on individual coding skills and implement your own systematic strategies to supplement your proprietary trading. Good sense of morale between traders, socials and drinks.
Cons
No salary, commission based. Management may take a focus on hiring new people compared to developing you as a trader. Infrequent feedback from superiors, this will only happen once you succeed which can be counter intuitive to new traders. New starter training is brief and only reviews exchange specifics, it does not specify company specific edge that can improve trading.