Pros
The one good thing is the ability to be in the company of other HR professionals - something that is rare once you get past entry-level HR, unless you are in a very big company.
Cons
The executives have NO understanding of HR. I was actually told by a member of the management team, in a wine-induced state of candor "I have no idea what you do all day." That might not be so alarming if not for the fact that these executives were in the midst of decisions about how to staff the client services team. In the end, they chose to greatly increase the client load on the client services team, providing maximum profitability. Consequently, the rate of turnover among the HR consultants who support the clients is unbelievably high. One colleague put it well on the way out "I'm tired of starting every client conversation with 'I'm sorry '". It just wasn't possible to provide good client service with the workloads that were assigned in the run up to the IPO, and that continues to this day. The result has been a mass exodus of HR services professionals, and a backfill with less and less experienced consultants. And the reputation among their clients continues to degrade - constantly changing HR reps, poor service levels and inaccurate and incorrect guidance. You can't blame the HR consultants - they are being set up without possibility of success. But you certainly don't want to join them.