The first thing that comes to mind is the sheer number of crash reports they were getting early on. I know I submitted probably two dozen myself those first few days. Game is rock solid for me now, though.
The second thing that comes to mind is that they are clearly sucking up a whole lot of data around gameplay. The stats they published on Friday about how people played opening weekend was eye opening to me regarding the amount of data they are ingesting: https://steamcommunity.com/games/1086940/announcements/detail/6199820457241938860