Watching the digital foundry video, the tech seems to work well enough. People are underestimating immediacy and access. We're on YouTube so often anyway. Everyone is still in the same place on mobile, though Google owning play store will be a big deal. Lots of advertising for AAA games on mobile now?
That said, I don't go to video sites because I want to do anything gaming related usually. Maybe Cortana on edge or desktop could provide that same push to the end user. Now that it's going to share a lot of code base with Chrome, I hope features like that stick around.
Anyway, I don't think this is DOA, but I also think it depends on how easy it is for developers to get involved. Are these standard PC versions of games? Or is every one a bespoke UWP-like entity? If it's the first, MS should accelerate 1st party or do some sort of announcement to go with xCloud news. If it's the second, Google will be abandoning this in a year and a half.
Edit: guys, looking at the wall of partners for stadia.. Just realized I see simplygon and visual studio and havok on that wall. Interesting how Microsoft probably knew much more about this much earlier than I would have thought. Unless there was really really strict compartmentalization.