Pros
I worked for Deltek for 4 years as a Senior Enterprise Project Management Consultant. The pros of working there is that they are the software developer for Cobra, which is what I consulted on. So I had good access to technical support and senior management in case I needed it. I always felt supported in my work.
Cons
There was apparently high turnover among the company's software developers. Since there didn't appear to be any developer that really knew the software well, it was common to find that bug fixes caused new bugs to arise. Also, I've seen that some consultants like to be a "lone wolf" who goes in alone and never has anyone managing his work. There are several layers of management, so you cannot be a lone wolf with this company.