Pros
Its a recognized name and looks good on the CV. The opportunities for renewal are good (I was a contractor). You can work there as long as you want (providing you are competent). The money is quite good but not the best to be had.
Cons
The place just has a really stuffy atmosphere. There is generally no impetus to get things done or go about self improvement amongst permanent employees. There is no common vision of delivering a good product on time and in budget amongst employees. I kind of get the feeling they think its a right to work there and that they can get money for just turning up to work without actually delivering anything. Its a pretty depressing atmosphere at 8 Canada Square and the air conditioning (or lack of a decent one thereof) tends to get people down. I personally have not worked at a place I found more depressing and generally soul destroying. This is a great shame.