Pros
They've led a lot of big companies to believe that what they are providing is of any value. So you can end up in a big company which doesnt necessarily mean that you'll stick around. Remember big companies are hiring though them because they can easily get rid of people without implications. Plus if their clients knew how unhappy FDM employees are they wouldn't do any business with them. Nobody wants frustrated people on the job!
Cons
1. O boy... Training is BS... 2. You are constantly being lied to that you can't get paid overtime when you can and you must. All of the sudden when your contract end date approaches and if the client wants to keep you onsite they will start to get "oily" and a lot of things "that were impossible in the past because of the client" are now easily doable. 3. Almost certainly there will be an error in your last salary (I've spoken with a lot of people that have experienced this) and they will stop replying your emails. 4. All their dodgy clauses in the contract are in the employee's disadvantage. Like that you are obliged to work up to 48 hrs a week if required (incl. weekends). For me, personally, this company must be sued for being immoral and the worst thing is that FDM takes advantage of young people and recent graduates that are simply trying to find their first job and easy to mislead.