Pros
Generally the people are quite nice and laid back. It is beneficial especially if you need to complete a qualification such as ACA, CFA or part-time masters.
Cons
Things are run pretty inefficiently there and the pay is almost always below the industry's average... They keep pushing for this flat and transparent hierachy, which ultimately means no promotion until you are almost retired. If you have the luck of working in the headquarter, unless a) you work in one of the 3 trading floors and b) you come to work during those god forbidden hours (very early in the morning, very late at night or weekends), fighting for the lift can be quite a nausea experience. In some departments, you will find these obscenely well-paid contractors who don't add much value.