Pros
Various types of projects to work on. Some excellent people to work alongside, very good technically etc. You can drive a path for yourself, if you're self motivated enough.
Cons
No real career progression, even though they say there is. Line management can be poor, it depends greatly on where you're place. T&Cs are pathetic to be honest. When working on site you have to buy your own lunch! No overnight subsistence allowance. Everything relating to HR is off shore, and the India centre doesn't work "off script". You end up in the same disputes over expenses over and over again. Overall culture not great - you feel like a number, not a valued employee. Getting training is difficult, there doesn't seem to be an appetite to invest in the staff.