Oh, this is disappointing, even if it is early days.Relevant snippets from The Verge review:
With Destiny 2, it’s even more obvious that the game isn’t running at the highest settings. On a Chromecast Ultra, a “4K” stream looked closer to 1080p, and my colleague Tom Warren and I swore that the 1080p streams we were getting in the Chrome web browser looked more like 720p.
Initially, Google told us that it was using the highest-resolution, highest-fidelity build of Destiny 2 available. But Bungie later confirmed that our eyes weren’t deceiving us. “When streaming at 4K, we render at a native 1080p and then upsample and apply a variety of techniques to increase the overall quality of effect,” a Bungie rep said, adding that D2 runs at the PC equivalent of medium settings. That explains why the Xbox One X build, which runs at a native 4K and with higher-res assets, looks so much better than Stadia.
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I can’t truly tell you whether Google Stadia will work for you with as much fidelity as you see above because I live in Silicon Valley, a mere 45-minute drive from Google’s headquarters, with a fairly good 150 Mbps Comcast internet connection and an excellent Wi-Fi router at my disposal. I’m likely close enough to the company’s West Coast data centers that I’m probably akin to a best-case Stadia user.
Have they done any marketing, I'm not including to the small corner of the enthusiasts that already knew about it.
Maybe the actual launch will be next year