Pros
One of the best reasons I found working at PAREXEL is - if you actually try to do well - you learn a lot about rules and regulations governing clinical research. As a Phase I site, it is heavily regulated by the government and sponsors. This can make the experience stressful, but in the end it is so much more valuable. I have taken this knowledge of quality and compliance to my current position (still in clinical research) and have added tremendously to the work there in such a short amount of time. I owe this to PAREXEL and my experience there.
Cons
The management is awful. If you have any new insight, it gets shot down immediately. Thoughtful comments are met with, "This is how we've always done it. Thanks for the feedback, anyway!" How is this supposed to help not only the company grow, but the employee as well? I felt as though my voice was unheard oftentimes and this decreased my motivation.