Avantages
Some great people, pockets of real capability/expertise and also passion/ownership. Culture is slightly too laissez-faire, but better than some other large SIs. Pay/packages are not as bad as many people seem to think (usually those with less experience of working for some of the other large SIs), but recent loss of final salary pension and no pay awards have obviously been tough and unpopular.
Inconvénients
Too many senior people who don't understand the systems integration/outsourcing business, never mind just the desktop and service desk type work we tend to try and go for. Far too many people who simply don't care, do as little as possible, who wouldn't understand "ownership" if it bit them, and who never seem to suffer for it. Company policies on working from home, and working in "fragments" all over the place, mean that people can "hide" successfully for long/frequent periods. Poor adherence to any kind of process (I hate bureaucracy but sometimes it's just chaos). Lack of investment in internal systems - leading to huge internal inefficiencies.