Pros
GPJ has some of the sharpest people in the Event Business. You will be able to work on High Profile accounts with sizable budgets & dynamic teams. GPJ is truly a global company with 24 offices worldwide and now one of several agencies held under the Project: Worldwide. This is a good place to get your start in the Agency World & a nice company to have on the resume.
Cons
GPJ likes to call themselves an agency when what they really do is build exhibits & execute events. You will not being inventing new ad campaigns or even have any input with your clients on doing so because GPJ typically executes a plan that has already been planned either by the client or a large Ad Agency (ie Chiat, RPA). Probably most important, GPJ is not well diversified. About 70% or more of their business is in Automotive making it highly dependent on the performance of that industry. For example, there were huge layoffs in 2008 & 2009 for no other reason than the severe contraction of the Auto industry.