Pros
Nice people, motivated Partners. A large proportion of staff have been there a long time, which reflects well on the company. But there is a healthy influx of new staff, at all levels, as well as those returning. Policies and procedures are exemplary, but are what is now expected by key global clients. Company sets itself apart from the other global consultants (who are mainly engineering based) by being focused around Sustainability. Client base and project work is second to none.
Cons
Maybe some work too much but that is because they are driven individuals, it doesn't reflect any requirement from the company. They would no doubt work too much anywhere else. I think some of the reviews on this site are too harsh, and reflect the reviewer not ERM. You will probably find the world is not as rosy a place outside that you think it is. You need to develop your own career, it won't be put on a plate for you; the company doesn't exist for your benefit.