This is a great product, I'm... mostly happy with it.
MS is moving away from the incredibly deep UWP integration as it moves towards an open, cross-platform ecosystem. That's understandably going to take time to unwind, and it makes sense that they'd start with product offerings and then move to more technical application. This means that even though the Game pass product is available and great, it's still got DEEP UWP hooks that are a quality of life issue for PC gamers.
Currently, users are unable to access game files and configurations, and UWP controls game behaviors with streaming, multitasking, and so on. That new Apple TV controller support and Steam Link app aren't going to be compatible with this platform until apps are no longer deployed in this manner.
Still a good product IMO, and while I don't expect MS to unwind the UWP integration on existing titles, I expect the platform will work a bit more like steam and give the user more control in the future. Though, maybe they'll keep it locked down tight to retain parity withi the Xbox for things like cross platform saves. Who knows, but it's a step in the right direction.