Pros
Very relaxed and non-heirachical work environment. Peers are very friendly and meritocratic. Management respect you for what you achieve, not because you work long hours or brown-nose. Their technology and theory is more advanced than most people realise. Gives capable people a chance to get a foothold in banking who might otherwise not have had a chance just because they "aren't the right type". A good place for people who've done the hard-work and long-hours thing in other banks to work if they want a better work/life balance.
Cons
The only way to get a market rate salary/bonus is to go into the job market and get an offer. This will often be matched, but people often take it as an opportunity to move which leads to quite a high turn-over. It is common to find people joining from outside banking and moving on to a second bank within 18m to 2y - though some people like the comfortable life-style and stay in the same job for years. Management on the business side dominated by the French, and although this gives them a different style than people might be used to they are generally good. IT management is often made up of people who wouldn't be promoted elsewhere. Some have worked out, many haven't.