Pros
They seem like they care about you and what's best for you, they get super involved with meeting you face to face, they ask a lot of questions about you, you meet or talk with a recruiter, a salesperson and sometimes a management person, recruiters and salespeople do a good job of preparing candidates for client interviews, they stay in touch and follow up during assignments, they pay 100% of employee Medical and Dental benefits, they match 5% of my 401k, responsive and organized back office staff
Cons
For people who don't like meeting and talking with a bunch of people and having all of those people involved with trying to get you a better job, then their style might be too much for you. But if you like a lot of personal care and attention, this isn't a con.