Pros
Lots of passionate people who love playing games, along with a well stocked kitchen and cafe. You won't go hungry here, and can always find someone who has played some obscure title you think only you've played.
Cons
Riot went through a hyper growth phase where hiring decisions were very rushed; this resulted in a wide band of talent, very hit or miss. If you're lucky to have a good manager, you're good to go, otherwise, you'll find that your passion for the product, the company, and the industry will quickly disappear. A lot of managers have never been managers before, and some are afraid that the people they're managing will overtake them or make them look stupid, so a lot of brilliant talent end up finding other opportunities, leaving only the insecure managers and resulting in a cyclical decline in talent density.