Pros
Good amount of training opportunity and opportunities to make connections as they have hundreds of thousands of employees all over the world working on many different projects.
Cons
It feels like you're a number. My raises lagged inflation by quite a lot. Also I had a closer relationship to the company I was on contract with than Cognizant. Cognizant would just check in on me every now and again, which that might be a pro for some, it's a con for me because they wanted you to do a bunch of added work and projects for them and incentivize you to do it with higher bonuses. Again, this sounds like a pro to some, for me it was a con because I already had a commitment to the company I was on contract with and plenty of work to do for them.