Pros
Think HQ is filled with some of the greatest people you will get to work with. Genuinely caring people to spend your 40 hour weeks with.
Though everyone comes from different disciplines, there is room at the table for everyone's experience, and the diversity in briefs and projects allows for all teams to lead and flex their respective muscle.
In my nearly five years of working there, it was extremely rare to have to work longer hours (unless a prior agreed event or engagement) even in times of busy briefs, new business etc. A work-life balance is celebrated, and managers look out for their line reports well being.
Above all, there is opportunity galore - if you have the appetite to go after them. It's an environment where initiative is welcomed. If you have an idea and want to make it happen, you'll get the support to do it.
An environment for go-getters and genuine team players.
Cons
As with all agencies, workload and priorities ebb and flow. If you don't want to have to be flexible or agile in your work, then maybe not the best place for you.