Pros
Take the negative reviews with a grain of salt--they are mostly a consequence of company size. Up until 6-12 months ago we were a "small" firm and it's uncomfortable to write a review as a happy current (or former) employee when everyone (in your branch) will know you wrote it. This leaves the most likely people to write reviews to be bitter, former employees. Given that we are now a mid-sized firm I would encourage employees (former and current) to give an honest review of the company.
Pros:
1) Very intelligent coworkers
2) Competitive salary and benefits
3) Great work-life balance (for consulting). Work from home Fridays, multiple holidays, managers are very lenient with employees needing to come late/leave early/leave for an hour or two for an appointment. It mostly depends on how reliable you are in terms of getting work done on time and not being someone overtly trying to take advantage of C1's leniency
4) No traveling Monday-Thursday nonsense (i.e. our firm does more than simply sell employees to a business for 6 months at a time)
5) Opportunity to work directly with high-level people (i.e. Directors, Partners--most of whom are open to suggestions on project approaches, design, etc.). Really, this shouldn't be understated: you can quickly get visibility with the owners of the firm.
6) The firm makes a real effort to get you on project types you request to work on
Cons
1) Partners have very different styles of managing projects--mostly due to their areas of expertise and personality types
2) Recent split in NJ/NY office seems likely to cause more complications than it fixes