Pros
Riot Games is a place you can really grow both personally and professionally, taking on more complex responsibilities and owning whatever you can. People working here really do love their work and try their best to do what is best for the players in the long term, even when we don't succeed. Most managers do a great job of doing the small things right, from arranging celebratory dinners, to recognizing key contributors, to little things that acknowledge when you do a good job.
Cons
The truth is that your experiences at Riot will depend heavily on your manager, your team, and your discipline. Some teams are awesome with high levels of cohesion, while others don't have accountability or great work environments. It is really hard to call out any particular team or discipline as there are people in all disciplines who work selflessly, but the people who normally get ahead are those that are friends with senior management or who are directly hired into positions they aren't any more qualified for than people currently in the organization. It's a sad fact that people doing similar jobs in different parts of the organization get paid different amounts and many of the people brought in over the past year are paid more than the rest of us and aren't bringing any more value.