Pros
For a big corporate the company still allows people not to conform to cookie cutter office worker mould. People are friendly and decent - anyone cutthroat or unreasonable stands out as the exception not the rule. Good pay and conditions and (for the managers I've had over close to 10 years) a good culture of sticking to 9 - 5 ish, unless you progress to senior manager where much more is expected If you want to get on in the company there is a huge variety of roles and you would be supported well to do that.
Cons
Slow to act as a company which is frustrating, not very dynamic - not necessarily the place to be if you're very ambitious and want to see constant progress and development around you. Maybe more a factor of the industry as anything. Most other cons stem from the nature of 21st century office work for a large corporate and aren't specific to EDF.