Avantages
Trying to say something definitive about such a huge company is similar to an attempt to say something about the whole automobile industry based on your own car. If you got lucky you have a great car, if less lucky you will struggle with repairs all your life. Similar here, people who reach into the core development projects might get a chance to work on the latest technologies and implement critical mission systems. However, if you are less lucky, even if you've got a good IT background they might assign you a position to implement a bunch of business rules for a particular customer, which will end up in writing a bunch of if-else-get substring-close file statements, and you can do this for years. It also depends on the team and manager - people are different, so are the managers. Some will make your life better, and some will transform it into a nightmare. The key is to understand what is for you and what is not, and act accordingly. It is not a pure IT company. One who wants to succeed must possess border skills like attention to details, ability to talk to the customers and understand their needs, be proactive. People who are IT-only inclined will not find this company satisfactory enough, because the chance of getting into the core development is small. But those who are perfectionists, like to make the job done till the end whatever it will be, and also possess good IT skills will be those who will find themselves like fish in the water.
Inconvénients
Travel in economy class even during the long hours flights. Very long time to wait for a promotion.