Pros
Marshall Wace is a great place to learn fresh out of university, also generally early on in one's career. The setup is very collaborative and one can learn a lot quickly.
Cons
The firm relies rather heavily on the quant strategies for its bottom line, but there is generally little appreciation of quants by the senior management. I got the impression quant was seen as a sort of backwater. It compliments the main business but is not considered on par with the other front office teams. Maybe it's changed since but likely not. In a sense that is expected, given the firm's DNA is essentially in non-quant and fundamental investing. That is what has helped them grow into one of the most successful hedge funds at the moment. It is mushroom management a bit though. It's more keep your head down and keep producing good research. This setup has probably contributed to the large number of departures from the quant teams of people with up to around 3 or 5 years of experience. Normally over 80% of team comprise of graduates and people with a few years of experience. Beyond that level people generally move on elsewhere. I got the impression that management weren't particularly bothered by this situation. The churn is sort of factored into their hiring decisions. Like I said earlier though, it is a great place to be early on in one's career. As long as you approach it as such you are unlikely to be disappointed. The quality of people that work there is very high. I definitely do not regret the years I spent there.