I have no qualms about couch gaming with a KB+M if I can do it with my friends and my already extensive Steam library. Unless they completely drop the ball on this, I'm in.
The beauty of a PC is you can build whatever you want. It doesn't need to be large, and doesn't need to have LEDs. There are plenty of small form factor cases on the market with the same footprint as this one.
And enthusiast cases like this are often quite expensive and not easy to get. Then you need to think about thermals, and find hardware that actually fits.
You can approach it form another angle and treat it more like a NUC and get a SoC but then you're probably not going to get close in terms of gaming performance.
So long story short: I disagree that it would be straight forward to build something like this on your own, at the same price point.
We're more or less waiting to see if / how much is Valve willing to subsidy the price with the expectation to recoup it with software
And then you get your case and mobo and PSU and maybe CPU and your budget is already at over 1000€ and you still need a GPU.
Not a PC gaming expert though and I don't have infinite resources to spend on figuring out how many millimeters of space each specific case has and how long a GPU is =)
But I've seen enough horror stories where someone bought a GPU or a heatsink that was like 5mm too big and didn't fit in the case without a hammer.