Pros
The clients can be really great, but this could vary depending on your site. Some managers are really nice and will defend you and want to see you succeed. Your schedule depends on your site so if you're lucky you get paid holidays, weekends off, etc.
Cons
The health insurance is terrible. I lose a large portion from every paycheck and have to pay just as much out-of-pocket to see a doctor for 10 minutes. PTO doesn't roll over to the next year and coverage for when you can't come to work is limited. While some managers are great, some will take advantage of you and find ways to give you more responsibility that is above your title and salary without a chance of a raise or promotion. Even after a stellar review that encouraged upper managment to put me in a leadership role, I received nothing. HR is painfully slow and the training sessions they make you complete every quarter are a joke (unnecessarily long and full of out-dated or incorrect information).