Vantaggi
The only pro I can think of is that you'll make great friends here. This is because, for those who are in the same boat as you, you only have each other to make light of the situation. Friendships will go a long way. There's also a very supportive manager when you're not on the client site, which was our saving grace.
Svantaggi
It's not only as bad as you've heard, but the reality is worse. If you're looking to join because you are a graduate and like all graduates, being desperate for a job in your respective field... You will not get the relevant experience here. Training - In my case, the training was completely irrelevant and unrelated to what I ended up doing, putting me on a career path that I had no interest in; making me stray further from my aspirations and wasting my time. Clients - Are aware of your position of having no say, and will also look to deceive/exploit you. Can go months without the opportunity to attempt to join a client project (3 months max in my case), wasting huge amounts of your time.