Vantaggi
If you are good you WILL get placed - and that's a big point to raise - they will get you in the door of some of the best blue-chip companies. If you aren't so good, they can't guarantee you anything which is what I think a lot of people miss - after all you can't polish a turd. A lot of people go in there expecting to come out with a guaranteed job. This is NOT the case. You have to interview with their clients and then they make a decision based on what they think of you. As far as I could tell the development stream was the more successful of what they offer as I did not see a single developer sat around waiting for placement whereas those on PMO and FDA streams and even some testers and app supports took a little while longer. Of the people I trained with, all of us are now working in large IBs, blue-chip companies or world renowned organisations. If you had told me I would be doing that 9 months after graduating with a 2:2 I'd have laughed in your face. The rumour that you don't get over time is also untrue. That depends on your client. I have significantly increased the money I earn from doing weekends working remotely on call.
Svantaggi
Can rush you out the door to get an easy buck. Not the best communicators once you are out the door - only contact you if there is an issue and for their monthly newsletter telling you how great the company is doing (which has little or no impact on you) Low wages, but you can get bought out before your 2 years is up if you impress on site and from there its all uphill.