Pros
Blizzard makes great games and takes the process of that very seriously. Employees are very loyal to the company. Activision has limited influence into the decisions Blizzard makes. Players will worship you. You'll get to work with very smart people.
Cons
Blizzard doesn't work hard to be a great place to work. Essentially, it's a privilege to work at Blizzard and you will be reminded of that constantly. Management isn't a high priority. A lot of management in engineering, art and game design is farmed out to professional managers who aren't actual members of that discipline. I was told at one point to stop focusing so much on my direct reports and just make more good features. Blizzard has a rock star culture. This can be fun when you see your colleagues on stage at Blizzcon. It's not a great place if you believe in humility. Blizzard employees can experience Stockholm Syndrome. They are made to feel guilty if they choose to leave the company.