Avantages
The hours are flexible and the environment is relaxed. Nobody cares what hours you work, so long as you get your work done and are available. Additionally there is very little bureaucracy. If you want to switch roles within the company, management not only encourages it, they help you achieve your goals. Additionally, everyone is approachable. I've started up random conversations with senior management, and even chatted with the CEO once or twice in the hallway as he passed by.
Inconvénients
The work is challenging. Part of Riot's culture is that we expect everyone to push out of their comfort zone. While this helps to level everyone up, it also means that you will constantly be faced with new challenges, harder problems, and higher stakes. If you attempt something and fail, however, you aren't punished. You're expected to get feedback and keep challenging yourself.