Pros
First and foremost, the product is fun and exciting. I can't tell you how much of a difference it makes sitting down at your desk when you are working on something you care about. Secondly I'd say is the perks. There are plenty of gamer perks, party perks, and money perks as long as business is going well.
Cons
Culture is the biggest struggle for me. It is a big company so this may vary by department. In my department people tended to be cold, stiff, and terse. I'll walk by and throw a friendly what's up as I walk down the hall and a surprising number of people will avert their gaze and not respond. It could be me, but I've worked for several companies and this is a new experience. I'm also new to the area and was hoping to make friends to socialize with outside of the workplace but the people here tend to be homebodies. To their credit they do try very hard to promote social networking. This may be a problem that is outside of their control. The other note that I would make is that pay scales are not competitive. They would argue that they pay close to nationwide average for a given title. But what they don't say is that holding a given title at Blizzard is much more demanding then holding the same title at other employers and the cost of living is a very large pill you will have to swallow. Lastly, the cafeteria food is bland school lunch grade stuff and there aren't any alternatives in walking distance. Coming from a down town location, this was a surprisingly big pain point.