Pros
Free food, poker and beer on Friday, fast paced environment. High risk high return for those who were able to succeed.
The free food is great except that people gained weight over time.
The hours were crazy. I started as a night clerk and my hours were from 7pm to 6 am every night. After moving up to the day shift, it became 6am to 4:00pm. I learned a lot of things about futures trading, market making, treasury bonds, and risk management.
Cons
Long hours, high turnover of employees, risky business model. I was there for about a year and a half and I think the turnover must have been 20-30%. Some guys would show up one day and leave a week later. I guess it's good to know early if this is what you want to do.