I started my career at gravitytank. In that time, I grew tremendously because of the access to willing, savvy mentors. In my experience, everyone was there to develop the next generation of the team. I believe in the leadership team - they truly act in the best interest of the health of the company and team. It felt like a family environment.
Cons
It's consulting - so projects can be consuming, hours long and pretty intense work environment. They also grew quickly in the past 5 years, so there are some adjustments needed as the culture of a bigger organization develops.