Pros
I'm am a trader in Sydney and have been for several years. Things that have stand out to me are: -Well structured training program when you join run by a dedicated trader trainer. -Given a lot of responsibility as soon as you join a desk- Around 4 months in the job. You get paired with experienced trader(s) who will mentor you. -You will learn from some of the best in the industry. There's a reason Optiver has such consistently strong performances year on year. For example, 2017 was one of Optiver's best years- a year where most market makers struggled to turn a profit due to very low volatility. -Minimal hierarchy. If you have good ideas there's very little holding you back from executing. -Get to work on challenging quantitative problems that have a fast turn around time to see the results. -The mission statement of "We improve the market" is taken very seriously and means a lot to me. Practically this means we spend a lot of time trying to provide liquidity where it's actually needed (particularly in options and ETFs), help exchanges improve regulations to make them safer (think better error trade rules) etc.
Cons
Although the hours are reasonable by professional standards (10 hour days, no weekends), the work is intense. At Optiver you will be challenged to achieve beyond what you think is possible. I don't see this as a con because I find the work really enjoyable and stimulating. However if you aren't able to keep up or aren't passionate about working on these sort of problems, it will be not be fun.