Vantaggi
If you are in the early stages of your career (2-4 years experience), and are looking to work on IT projects at large clients as a developer or tester, you might want to consider Sogeti. It is fundamentally a Staff Augmentation firm (a.k.a Body Shop). They do not have projects where they can grow people into roles. So, if you are a fresher, Sogeti will not hire you. Or, even if they hire you, there may not be projects for you to work on. It all depends on which office you work for. So, if you get a job offer from Cincinnati or Dayton or Chicago, you may get to work on good, interesting projects. But if you were to work at offices with <150 consultants, then god help you!
Svantaggi
The business model is extremely unfavorable to consultants. Sogeti generates revenues - lots of it! But it generates revenues because Navin wants to send as much as possible to France. The business model is more of a body shop, covered in a "large reputed consulting firm". The training is bad, there is no emphasis on career development, unless you are in Cincinnati, and if you cant bring revenue, you cannot grow. While that may be true of all consulting firms (that you cannot grow unless you bring in revenue), what is bad is that you do not get support in your endeavor to reach the top.