Pros
Stable company for a consulting firm. Because it is publicly traded does not have the up or out philosophy of consulting partnership. Working for federal clients also allows for great hours. basically 9-5 on most projects. Most projects are long-term engagements typically lasting 1+ years. It is not all body shop - augmentation work as i have been involved in a couple of strategic short-term projects over my short stint here. But Most work is implementation/outsourcing IT work. I find most people at this company are more humble and less competitive(negative competition that leads to backstabbing)than at my previous employer.(Deloitte Consulting) and the company has a more flexible culture than my other previous employer.(IBM Consulting).
Cons
I come from a private sector consulting background so i find the hours that i have experienced so far at CGI to be rather pleasant. After working for companies who along with the client expected 60+ hour work weeks plush travel, it is rather refreshing working for a company where 40 hour work weeks is the norm. The low margins involved with government work are also reflected in the lower pay as compared to our private sector counterparts. But it is a personal decision to take less money for a better work-life balance. It's a decision that i decided to make and i'm quite happy with.