I expect to pre-order the hardware, but I'll probably hold off on a subscription until I see the games and have a compelling reason to pay a monthly fee. I don't really mind the difference between 1080p and 4K, so buying the games standalone seems like a nice fit for me personally, with the subscription sitting as a nice "premium" / improve-what-you-have option.
Personally, I already have an Xbox One that I lug around with me when I travel. The most compelling aspects of this are it feeling a lot more mobile (since you only need a chromecast and a controller, or just the controller with your phone), and feeling a lot more future-proof since it's effectively just a thin client running on beefy hardware elsewhere, that I expect to be upgraded to meet current game demands over time.
