I was part of the Project Stream test for Assassin's Creed Odyssey. I largely played on the super fast connection at work, and it played pretty well. It seemed better with a controller than a mouse and keyboard, probably because the controller naturally ate some of the latency.
The Stadia announcement showed some really neat integration as well -- playing kicks off the stream that you see as well as an ultra high quality of it to your YouTube gaming channel, viewers can queue up to play against you, you can fire off a link to friends and have them load up in the exact scenario you're in to challenge your score, compatibility across almost any device that can run a web browser or receive a Cast, etc.
That said I think the biggest hurdle is convincing developers to make a Linux / Vulkan port of their games. I'd personally love to get my hands on a dev kit.