Pros
Activision is a stable powerhouse built on a very conservative approach to making games. This means greater job security in tough economic times. Activision is also big enough to absorb some losses and find work for employees when a game tanks. If you're a good employee and you happen to get in with the right people you can move up quickly and draw a very competitive salary. The royalty structure is also a nice addition.
Cons
As Activision grows its becoming increasingly corporate in many ways. This may be a positive for some people, but most creative types I work with and myself find it increasingly stifling and stuffy. I think the growth has outpaced the competence of the management, and often bad decisions from the top seem arbitrary and counterproductive. Morale is really up and down at some studios. There is just a bit too much cronyism for my taste as well.
