Pros
It is a good place for students to find summer work, along with anyone else that does not have a college degree. They offer various assignments that differ greatly in work hours, so finding a position at a company that has hours that will not conflict with activities or summer courses will not be too difficult to do. You also can start working very quickly, I started my position less than a week after I first walked in to find out what kind of positions they were looking to fill. All of the staff I met were very helpful and nice.
Kontras
There are not always a lot of jobs to choose from and they may not provide you any experience for the future. I was in school for a bachelors in business but was unable to secure a position with much relevance. Many of the jobs are manufacturing based rather than office based. Also, many of the position they were trying to fill at the time I applied were 2nd or 3rd shift, which I had no interest in. Many of the jobs are quite short term, and I believe almost all are only temporary positions. You also don't get paid as much as you would working directly for the company you are contracted to.