Cloud gaming isn't new and it has been around for some time. When it was first started, it was ahead of it's time as the internet connectivity and infrastructure weren't ready for it.

With Google stadia it might be different since the company has so much control over the infrastructure. So my guess is performance won't be so much of a hit.

The concerns over games-as-a-service and data usage are still valid though. I guess the service isn't meant to target hardcore gamers? But rather occasional gamers who are not willing to invest too much on gaming hardware?