Pros
C1 has a great reputation among its clients for doing high quality work, which is essential for anyone interested in going client side after gaining a few years of consulting experience. Moreover it's good to feel proud of your deliverables and it keeps you motivated to put in your best effort. Work/life balance is pretty good keeping in mind this is a consulting firm. The best part is that travel is minimal (maybe once a month) and every Friday is a work from home day. So even though weeks when projects are due can get rough during the weekdays, you will rarely have work that carries over into the weekend. The average workweek is between 50-60 hours. Management cares about work/life balance and has policies in place to make sure no one burns out. C1 is a fast growing company. In the year that I've been here we have expanded from 4 to 6 offices and expanded our headcount by 30%. There are lots of opportunities for career growth at C1 and promotions are based on merit as far as I know. The bad reviews on glassdoor are either untrue or were true at some point in time far in the past. Nobody that I know here has had bad experiences at C1. All my co-workers are genuinely authentic and friendly. I would say we almost have sort of a startup atmosphere in the office where we are part of a family.
Cons
Each office usually works with local clients in the area, which can mean many repeat clients. In general the diversity of clients at C1 is not as great but in part that is due to our size and niche market. Weeks when multiple projects are reporting can get rough. Management usually tries to avoid staffing people in that way but sometimes there's no choice. Since most projects are 2-3 months in duration, and people are staffed on 2-4 projects at a time, the reporting weeks for some projects will inevitably overlap. The good thing is that if you have consecutive weeks like this you get a comp day in return. Lastly the salary at C1 is a bit below comparable salaries at the big consulting firms. I think this is fair given that the workload is not as crazy as some of the bigger firms and given that C1 is not as recognized in industry circles as the bigger firms.