Pros
GMR has a good name and reputation within the industry. Strong client roster. Work hard, play hard. There are a lot of quality people that work there. It can be a fun place to work. Fair amount of perks. A solid stepping stone based on the quality of your clients and connections within the industry.
Cons
Too top heavy. If you didn't start in the early 2000s, you will not reach VP level or even director very quickly. They pay is mediocre. They do not do a very good job of identifying talent and often force square pegs into round holes. They have lost a tremendous amount of talent in recent year and have failed to replace with equal talent or fill those positions at all. Very lean and will work you to the bone. Very NASCAR centric. Often afraid to step out of their comfort zone. A lot of your experience as an entry level employee or even pre-VP is dictated by your VP. They range from people who are incredibly strong (and might not be around much longer) to people who are only concerned about themselves and have little concern for your career or serving as a mentor.