Almost unknown outside of the financial/ consulting world if you're not in France. And even in this world, its reputation is even if good, not excellent.
A culture of presenteeism, at least in Luxembourg, people stay even if their work is done. You can still leave but it is frowned upon. Some partners are wandering around the office every once and a while to see who is taking a break, who is leaving early and see who is still tworking after the traditional working hours.
You'll be doing a lot of additional hours and unfrotunately only a very tiny percentage of those will be counted.
There are not a lot of social events that are organized and you can't expect as many additional benefits as you would be able to if you would work for a big 4 company.