Pros
E&Y offers a good notoriety on your resume and is definitely a place where you can learn much about various industries and business issues solving (Advisory Services). The salary is a good average on paper (before considering weekly hours). I am convinced that Paris office is a specific case and that EY offers much better work environments in some of its other offices.
Cons
Very poor humanity from HR. Omertà rule, "everything is going so well" even when the open space is full of staff due to the lack of business from the financial turmoils/economic downturn (08-09). You actually get informed that you are fired through a "departure process" email in the morning (happened to several of my colleagues in 2009 as well as to a friend of mine in 2012 = consistent HR methods throughout the years). Falsification of individual reviews when needed in order to support layoffs. Bad corporate culture specifically in Paris office, very elitist culture (useless and counterproductive). Some Senior Managers you have been working with for several weeks ignore you when in the same elevator (do not reply when saying "hi") = common practice throughout all services. These subjective aspects do affect your perception of the organization after several months. Getting rid of this culture would improve the work environment so much!!! Huge weeks. The average week is 60 hours, minimum is 50, peak at 75-80 hours (work from home during weekends on a regular basis). You might get disappointed when comparing to your salary, realizing you make the minimum hourly rate with a M.Sc. and having been through a very selective recruitment process. Quite political. Promotions are usually based on "who you know" rather than "how you perform".