Avantages
Working for Riot was a very cool experience. I worked as a contractor for the eSports team maintaining the front end of their website throughout the week, primarily during LCS broadcasts. Most of the people there are smart, talented folks that are passionate about the product and Riot as a whole. Everyone sort of shoots from the hip, which is fairly typical of both broadcast and game development environments, so be ready to learn and adapt on the fly.
Inconvénients
Training for minimal, but not ineffective. You're sort of at the mercy of your direct superior, so if you get assigned to someone that's on the flighty side, you run the risk of getting marginalized pretty quickly. Upper management will barely know you exist, and chances are you'll get blamed for anything that goes wrong, even if you had nothing to do with it - that's just the life of a remote contractor. Also, hours were sporadic at best, and downright awful at worst - long graveyard shifts during major Asian tournaments are very common. And promotions aren't all that common. In general, it seems Riot brings in new talent to fill positions rather than promoting lower level staff.