Pros
As with any organization, B3 management can be frustrating at times, but as both a consultant and a project manager I've always felt like they had my back. They treat employees fairly and ethically, even in times when (as happens with client work) an employee has been removed from a project without justification. This is not to say that B3 condones poor work, but rather they have the capacity to independently evaluate their employees true skills and abilities and re-assign them to other projects as appropriate (but this does not mean they hesitate to take action when warranted).
Suffice to say B3 is not a throw-you-under-the-bus-and-back-over-you-at the-slightest-hint-of-trouble type of organization.
B3 has a good understanding of the client and their needs.
They allow their consulting teams to do their jobs with minimal interference.
Good camaraderie; in general, just nice people to work with.
Speaking from first-hand experience, subcontractors are also treated as partners and colleagues.
Cons
Not a training or mentoring organization, rather, a company who primarily hires seasoned professionals who do not need significant training. Not really a con unless you are junior-level.
As a small company, there are relatively limited opportunities for the direct charge (project) employees once a contract has expired.
No bonus or incentive programs, but good base salary.