Pros
The vision is great, it is on paper at least a global company, the products are cutting edge. Footprint is there in all the traditional industries, Dassault is present in all the major accounts of these traditional industries. Benefits are good, at least in head quarters in France. Travel is business class for trips over 4 hours, it is a wealthy company and it shows. Once you have a position, you can do pretty much what you want to do (at least as middle management level and above). With the right position, you get to travel all over the world and do a pretty interesting job. If you like technology, it is a good place to be.
Cons
There is absolutely no career management whatsoever. That is unless you are somehow related to someone at the right level at Dassault Aviation, Dassault Systemes or a major client. Since the company is after all not that big, it seriously limits the number of available positions. Culture is difficult to assimilate, and it is rare to have people hired with a good background (say at least 15 years experience) staying more than two years. Benefits are good in France but standard elsewhere, pay is below market. Company reorganizes each year, which does not give one the time to grow in a given position and prove their value. Also, it is easy to be out of favor and disappear in the crowd, examples abound.