Pros
Great way to obtain lots of useful skills like project management and client development. You can learn a lot through this firm. Some more reasons are that the firm can give you many opportunities to do jobs that most firms would not allow you to do without more experience. I am able to work with the client on work that normally would be reserved for more seasoned staff. Some of the people that work here are talented and a real pleasure to work with. I am paid reasonably well considering my little experience. Also, working here looks good on resumes.
Cons
Your time is not well respected. We are not compensated for the amount of time that we spend traveling to the client which can be significant. It is very easy to devote a year or more of your life to one client with little change in role or duties. I have wanted to look for other roles but I can not leave my current one because the client wants me to stay. Also, this is a very social-oriented job in that if you are not actively networking with others in the firm, you might not know about upcoming projects or roles.