I would say that the the training is intense and not everyone is capable! I have witnessed one person get asked to leave after failing the UNIX exam three times. The best thing about FDM will be your colleagues, you will have to be there for one another to make it. One week to learn a new skill and pass an exam / complete a project makes this process challenging... but who doesn't like a challenge? Further, the training isn't incredible, to pass the exams and finish the projects first time round you should prepare on the weekend ( worked for me).
If you are a highly motivated individual and have a strong work ethic then there is no reason why you wont do well with FDM. Just keep in mind that you are given three shots to pass an exam or project, if you fail your third attempt it's game over.
Some FDMers obviously feel they are entitled to more but I think these fresh graduates are getting ahead of themselves, they were informed at the start about the contract and the rules. There are no surprises it's your fault if you the sign the contract but then decide the contract isn't for you.