Pros
Mercer (still) has an excellent brand name and reputation. Though recruiting is run by admin staff and has mercurial management influence, it's very choosey. In New York, it brings in top Cornell, Yeshiva, Rutgers and Columbia grads, so it's a stimulating place to begin a career. Don't stay more than 2 years.
Cons
A shadow of what it was. In 2009, all the top performing partners left, followed by a delayed exodus of the analyst staff in 2010. The NY practice rebuilt and has a handful of good stories, as people learn compensation analytics. All other practice areas are in the dumps. Rather than address any of the underlying issues, management did more or the same, just instituted tougher controls on an otherwise low-performing partners/principals ("duds").