Pros
I had the time of my life at Seilevel (now ArgonDigital). Although I am no longer with the company, I look back on it with fondness and happy memories. The people who work there are all bright, helpful, and have the highest integrity. Their leadership is outstanding, transparent, and truly listens to their employees. It's a very rare company that has such an intersection of great leadership, talented people, and interesting work. Their mentoring program sets them apart from most employers and they have a very well-defined career path all the way from the most entry-level positions to the very top.
Cons
Like any other professional services company, sometimes the project you are on may not be your favorite, but the company truly makes an effort at employee satisfaction in this area. This is not a con of Seilevel per se, but of any company which provides consulting services.