Pros
This is a job that I find myself appreciating more in retrospect than I did at the time. Having the ability to work with many different clients and see how their business is run is the kind of experience you can't get in a classroom. The relatively small size of Mann Consulting also guaranteed lots of facetime with the founders of the company, who had lots of experience to share. The small company size concentrates the amount of experience you get into a shorter amount of time. I've found myself using many skills and experiences from this job in later positions as I manage others and work with my own clients, including examples and metaphors from the company founders. The founder also was a great teacher about the value of databases, systems, and efficiency.
Cons
Working for a small company is not for everyone - there's nowhere to hide. Unlike a large company where a new and junior hire rarely sees senior management, you will interact with them every day at this job, and that can be intimidating. The founder/CEO is fair, but not afraid to be critical. Also, in a world of startups with lavish perks, this is a somewhat more austere working environment.