Pros
FDM's clients are big names and do wonders for a CV You get exposed to some pretty wide scale technologies learned so much in my six months on site compared to a friend did working for a smaller company. Good graduate pay for most places in England You make a lot of great contacts and meet a lot of great people.
Kontras
Unpaid training period is one, especially if you don't get signed off right away. FDM market themselves as a clear cut solution, once you join that's it your certain to get a job. This is not the case. You still have to work hard and you are still competing against other trainees for jobs. Do not expect everything to be handed to you on a silver platter. Requirement to be flexible in location (Could be a pro if you like to travel) First year pay is not that great when you compare it to graduate rates in London