Pros
ERM is a very well respected organizations with some of the best experts in the field. You get the opportunity to work on a wide variety of different projects, even those outside of your business unit and join groups/think groups based on your areas of interest.
Cons
I really wish someone would have explained to me the internal ops structure at ERM before I accepted my position. I felt like I was apart of a high school popularity project trying to prove to others my qualifications and how much I could contribute to a billable project. ERM has a lot of very talented employees that underutilized the benefits and skills they could have brought to the table. Another huge con was the fact that your performance is basically souly focused on how many billable hours you were able to get, which required sucking up to partners to try to convince them to take you on a client project. All work outside of that is poorly valued which makes things hard starting out.